















































































































































































































































































































































































































































































•. 

* 

. 


' 






















PUBLIC WATER-SUPPLIES. 


REQUIREMENTS, RESOURCES, AND THE 
CONSTRUCTION OF IVOR NS. 


iV 




BY 


F. EL TURNEAURE, C.E., AND HP L. RUSSELL, Ph.D., 

*\ \ 

Dean, College of Engineering, Professor of Bacteriology, 

University of Wisconsin. 


With a Chapter on PUMPING-MACHINERY 

U / , . J 
,v v ’ V Sn 

By D. W. MEAD, C.E., M. Am. Soc. C. E., etc. 

% - 

# * 


FIRST EDITION. 
FOURTH THOUSAND 


» 

> 1 1 


NEW YORK: 

JOHN WILEY & SONS. 

London : CHAPMAN & HALL, Limited. 

i9°6. 


rp3+s 

T qio 

jqOk 


Copyright, 1901, 

BY 

F. E. TURNEAURE and H. L. RUSSELL. 


‘Gift 

Sidney B. Hfll 
Oct. SI J 93F , 

\ 



1 v 




ROBERT DRUMMOND, PRINTER, NEW YORK. 


PREFACE. 




The present volume has been prepared with particular reference 
to the needs of teachers and students in technical schools in which the 
subject of Water-supply receives a considerable amount of attention. 
The work is based chiefly upon the experience of the first-named 
author in teaching the subject for a number of years in the institution 
with which he is connected, and has been written with special refer¬ 
ence to use in his own class-room. 

In the discussion of the various subjects treated, the endeavor has 
been to lay stress upon fundamental principles rather than upon details 
of practice, although methods of construction have been freely given 
where they might serve to illustrate the principles involved or bring 
out the effects of differences in conditions. With the same idea in 
mind, many problems, usually treated empirically, have been subjected 
to analysis, more or less crude, but useful for calling attention to' 
certain general laws and limitations. It is believed also that such 
analyses may often be of much assistance in utilizing the results of 
observation, and that, if properly applied, they will aid much in the 
cultivation of the judgment. The necessity for the designer to keep 
constantly before him the question of true economy has been frequently 
emphasized, and to aid the beginner a brief general discussion of this 
subject has been given in Chapter XI. No apology is necessary at 
this time for the comparatively full treatment given to the subject of 
the Quality of Water-supplies in Chapters VIII, IX, and X. The 
authors have felt that the great importance of questions relating to the 
purification of water requires a more thorough presentation of the sani¬ 
tary phase of the subject than has heretofore been customary in works 
designed for engineers. The subject of Ground-water has also 
received considerably more attention than is usual, but, it is thought, 
not more than the importance of the subject will justify. 

References to authorities are numerous, and the plan has been 

iii 



IV 


PREFA CE. 


adopted of giving, at the end of each chapter, a brief list of the best 
literature of the subject treated. It is believed that this feature will 
prove of value not only to the student, but especially to the young 
practitioner who finds it necessary to make a special study of a partic¬ 
ular branch of the subject. According to the authors’ view, there is 
no branch of the profession in which a good working library, consisting 
largely of periodicals, is more necessary than in that of municipal or 
sanitary engineering. 

To the water-works specialist there is doubtless little that is new 
to be found in this work, but it is hoped that the form in which a large 
amount of widely scattered information has here been presented will 
prove of convenience to this class of readers. 

With regard to the authorship it is proper to say that Chapters 
VIII, IX, and X are by Prof. Russell; also several of the articles of 
Chapters XIX to XXIII, which relate more specifically to bacterio¬ 
logical and chemical features. The remainder of the work, with the 
exception of the chapter on Pumping-machinery, has been written by 
Prof. Turneaure. 

The authors desire to acknowledge their indebtedness to the various 
engineers and water-works officials who have kindly responded to 
requests for information. They are also under special obligations to 
Mr. C. B. Stewart, Assoc. M. Am. Soc. C. E., for a very thorough 
investigation of the literature of the flow of water in pipes, the results 
of which appear on pages 227-234, including the diagram of Fig. 34. 
Of the large number of original articles and papers which have been 
consulted, a great many have appeared in the Engineering News , 
the Engineering Record , or the Transactions of the American Society 
of Civil Engineers; and to the publishers of these journals special 
thanks are due for many of the illustrations which appear in this work. 

F. E. T. 

H. L. R. 


Madison, Wis., March, 1901. 


CONTENTS. 


CHAPTER I. 

INTRODUCTION. 

PAGE 

Historical Sketch.— Water-supplies in Ancient Times—Water-works of 
the Romans—The Middle Ages—Development of Modern Water-works 

in Europe—Development of Water-works in the United States. i 

Value and Importance of a Public Water-supply.— Domestic Use- 
Commercial Uses—Public Uses—Literature ... 12 


PART I. 

REQUIREMENTS AND RESOURCES. 

A. Quantity of Water Required : Sources of Supply. 

f 

CHAPTER II. 

QUANTITY OF WATER REQUIRED. 

Nature of the Problem—Consumption, How Stated—Influences Affecting the 
Consumption per capita—Consumption of Water for Various Purposes— 
Total Consumption per capita—Increase in Consumption—Variations in 
Consumption—Consumption in European Cities—Growth of Cities—Lit¬ 
erature . 15 


CHAPTER III. 

SOURCES OF SUPPLY. 

Classification—Quality of Water from Various Sources—Utilization of the 

Various Sources . 36 


CHAPTER IV. 

THE RAINFALL. 

Measurement of Rainfall—Rainfall Statistics—Mean Annual Rainfall—Secu¬ 
lar Variations in the Rainfall—Mean Monthly Rainfall—Minimum Yearly 


v 







vi 


CONTENTS. 


Rainfall—Maximum Rates of Rainfall—Extent of Great Rain-storms— 
Literature. 


CHAPTER V. 

EVAPORATION AND PERCOLATION. 

Relation of Evaporation and Percolation to Stream-flow and to Ground-water 
Evaporation from Water-Surfaces. —Influences Affecting Evaporation — 
Experiments on Evaporation from Water-surfaces—Calculated Evapora¬ 
tions from Water-surfaces. 

Percolation and Evaporation from Land-surfaces.— Influences Affect¬ 
ing Evaporation and Percolation—Effect of Vegetation or Other Soil¬ 
covering—Experiments on Evaporation and Percolation—Evaporation 
as Determined from Stream-flow—Amount of Percolation over Large 
Areas—Literature. 


CHAPTER VI. 

FLOW OF STREAMS. 

General Methods of Procedure—Influences Affecting Stream-flow— Units of 

Measure—Division of the Subject. 

Minimum Flow. 

Maximum or Flood Flow —General Considerations—Data of Maximum 
Rates of Flow—Formulas for Flood-flow—Rational Method of Estimating 

Flood-flow—Diagram of Flood-flows—Example—Some Great Floods_ 

Total Flow for Various Periods of Time. —Statistics of Stream-flow— 
Minimum Yearly Flow—Monthly and Seasonal Flow—Estimates of Flow 
—Effect of Lakes and Ponds on Stream-flow—Example of Estimate of 
Flow—Literature. 


CHAPTER VII. 

ground-water. 

General Considerations.— Occurrence of Ground-water—General Form 
of the Water-table—Porosity of Soils—Formations Favorable for the 
Transmission of Ground-water—Occurrence of Water-bearing Forma¬ 
tions.. 

Flow of Ground-water. —Methods of Determining the Flow of Ground¬ 
water-Formula for Estimating Velocity of Flow—Thiem’s Method of 

Determining Velocity—Quantity Flowing—Quantity Available. 

Springs —Formations of Springs—Yield of Springs. 

Artesian Water.— General Conditions—Use of the Word “ Artesian ”_The 

Character and Inclination of the Strata—Capacity—Predictions Concern¬ 
ing Artesian Wells—Important Artesian Areas in the United States— 
Literature. 


PAGE 

39 

52 

53 

55 

64 

66 

67 

74 

84 

89 

94 

98 













CONTENTS. 


• • 
Vll 


B. Quality of Water-supplies. 

CHAPTER VIII. 

EXAMINATION OF WATER-SUPPLIES. 

Scope and Extent of Examination—Necessity of Full Data in Interpreting 
Conditions—Collection of Samples—Sanitary Analysis of Water—Detec¬ 
tion of Pollution by Addition of Chemicals—Various Analytical Methods 


—Value of Different Methods. 10} 

Physical Examination of Water. —Color—Turbidity—Odor and Taste- 
Temperature—Chemical Reaction. 114 


Chemical Examination of Water. —Purpose of Chemical Tests—Expres¬ 
sion of Chemical Data—Interpretation of Chemical Data—Total Solids 
and Character of Same—Loss on Ignition—Chlorine—Organic Matter— 


Free and Albuminoid Ammonia — Oxygen Consumption — Nitrites— 

Nitrates—Summary... 117 

Bacterial Examination of Water.— Development of Methods—Scope of 


Bacterial Tests—Methods of Determining Bacteria—Quantitative Bacte¬ 
rial Analysis—Effect of Incubation-Temperature on Growth—Multiplica¬ 
tion of Bacteria in Collected Sample—Qualitative Bacterial Analysis— 
Number of Species—Significance of Liquefying Bacteria—Direct Physio¬ 
logical Tests—Value of Qualitative Tests in Comparing Waters—Anae¬ 
robic Cultures—Animal Tests—Concentration of Organisms in Water— 
Significance of Certain Bacteria in Waters—B. Coli as an Index of Sewage 
Pollution—Isolation of B. Coli—Detection of Specific Disease-bacteria— 
Isolation of Typhoid Organism—Isolation of Cholera—Disinfection of 


Polluted Wells and Pipes—Bacterial Control of Filter Operations. 123 

Microscopical Examination of Water.— Scope of Microscopic Exami¬ 
nations—Direct Microscopic Examination in Filtration-work. 136 

Sanitary Surveys. —Object and Value—Literature..... 137 


CHAPTER IX. 

QUALITY OF WATER. 

Importance of Quality—Changes in Quality Determined by Course of Water— 
Requirements as to Quality—Potableness—Water for Domestic Use— 

Water for Manufacturing Purposes—Distribution of Bacteria in Soil- 141 

Meteoric Waters. —Absorption of Impurities from Air. 145 

Surface-waters. —Character Determined by Nature of Underlying Soil— 
Surface-waters as Potable Supplies—Physical Appearance—Bacterial 
Condition of Flowing Streams—Self-purification of Streams— Causes of 
Self-purification of Streams —Dilution—Sedimentation—Vital Concur¬ 
rence-Unsuitable Food-supply—Aeration—Chemical Reaction—Conclu¬ 
sion—Vertical Circulation in Lakes—Bacterial Content of Open Surface- 
waters— Natural Purification Processes—Influence of Vegetation—Odors 

in Water-supplies—Influence of Freezing on Bacterial Life. 146 

Subterranean Waters. —Change in Quality Due to Percolation—Purifica¬ 
tion of Water in the Soil—Capacity of Soil for Purification—Extent of Fil- 










Vlll 


CONTENTS . 


PAGE 


tration Necessary to Effect Purification—Spring-waters—Well-waters— 
Bacterial Content of Wells—Effect of Pumping—Effect of Organic Nutri¬ 
ment on Growth of Water-bacteria—Artesian Wells. 161 

Effect of Storage and Distribution on Quality.— Improvement of 
Water by Storage—Impairment of Water by Storage—Effect of Distribu¬ 
tion on Quality—Literature. 169 


CHAPTER X. 

communicable diseases and water-supplies. 

Relation of Water-supplies to Disease Dissemination—The Germ-theory of 
Disease—Specific Nature of Water-borne Disease-germs—Diseases Due 
to Parasitic Worms. . 173 

Infectious Diseases Transmissible by Water-supplies.— Conditions Nec¬ 
essary for Infection—Water-borne Diseases Affect Intestinal Canal—The 
Most Important Water-borne Diseases—Typhoid Fever—Typhoid Fever 
and Sewage Pollution—Mohawk Valley Epidemic—Lowell-Lawrence 
Epidemic—Pollution of Lake-towns—Typhoid and Polluted Wells—Out¬ 
breaks Inaugurated from Single Cases—Typhoid Rates an Index of Qual¬ 
ity of Water—Diminished Typhoid Rates Incident to Improved Supplies 
—Seasonal Distribution of Typhoid Fever—Asiatic Cholera—Cholera 
Outbreaks traced to Water-supplies—Anthrax—Other Water-borne Dis¬ 
eases—Gastro-intestinal Disturbances—Dysentery—Malaria. 175 

Vitality of Pathogenic Bacteria in Water.— Conditions Affecting 
Vitality—Vitality of Typhoid Organism—Cholera—Anthrax—Literature. 191 

PART II. 

THE CONSTRUCTION OF WATER-WORKS. 

CHAPTER XI. 

GENERALITIES pertaining to water-works construction. 

General Arrangement of Water-works. —Classification—Works for the 
Collection of Water—Works for the Purification of Water—Works for the 
Distribution of Water—Arrangement of Works—Systems of Operation—r- 
Comparison of the Various Systems—Existing Works as Affecting 
Choice—The Dual System. icjg: 

Principles of Economic Construction.— The General Problem—Methods 
of Comparing Cost—Method of Capitalization—Method of Annual Ex¬ 
pense—Depreciation of Structures—Provision for the Future—Estimates 
of Cost—Literature. . 206 


CHAPTER XII. 

HYDRAULICS. 

Purpose of the Chapter—Units of Measure—Notation—Weight of Water- 

Pressure of the Atmosphere—Vapor Tension of Water—Pressure of Water 213 








CONTENTS. 


ix 


PAGE 

Flow of Water through Orifices.— Form and Proportion of Orifices— 
Flow through Small Orifices—Large Rectangular Vertical Orifices—Cir¬ 
cular Vertical Orifices. 216 

Flow of Water over Weirs. —Sharp-crested Weirs—Submerged Weirs— 

Weirs of Various Sections... 218 

Flow of Water through Pipes. —General Relations between Velocity and 
Pressure—Nature of Fluid-friction—General Formulas—Coefficients and 
Formulas for Cast-iron Pipes—Comparison of Various Formulas—Dia¬ 
gram Recommended for Use in the Design of Distributing Systems— 
Effect of Age of Service on Loss of Head—Friction Loss in Service- 
pipes—Coefficients for Riveted Pipes—Friction Loss in Wood-stave 
Pipe—Measurement of Flow through Large Pipes—Minor Losses of 
Head—Hydraulics of Fire-streams—Friction Loss in Fire-hydrants— 


Water-hammer. 225 

Flow of Water in Open Channels. —Formulas Employed—Measurement 

of Water Flowing in Open Channels.....,. 246 


A. Works for the Collection of Water. 


CHAPTER XIII. 

RIVER AND LAKE INTAKES. 

General Conditions-\. 249 

River Intakes. —Location—Intakes in Large Streams Varying Little in Stage 
—Intakes in Streams of Ordinary or Great Variation in Water-level—In¬ 
take-works for Gravity-supplies. 249 

Lake Intakes. —Location—The Intake Conduit—Protection-works — Ob¬ 
struction of Intakes by Anchor-ice—Literature.. 256 


CHAPTER XIV. 

WORKS FOR THE COLLECTION OF GROUND-WATER. 

Classification. . 264 

Works for Utilizing the Flow from Springs. —Objects to be Attained— 

Ordinary Forms of Collecting-basins—Methods of Increasing the Flow 264 
The Hydraulics of Wells. — A. Principles Governing the Flow into Ordi¬ 
nary Wells —General Form of Ground-water Surface—Derivation of 
Formula for Flow—Calculation of Flow—Effect on the Yield of a Change 
in the Various Elements— B. Principles Governing the Flow into Artesian 
Wells — C. Considerations of General Application— Pipe-friction and 
other Losses of Head—Effect of Depth of Well—Mutual Interference of a 
Number of Wells—Determination of Yield by Tests—Wells Sunk into 

Strata in which the Flow Takes Place through Fissures. 267 

Construction of Wells. —Forms of Construction—Location of Wells— 
Relative Advantages of Large and Small Wells —Large Ope 7 i Wells —Size 
and Depth of Wells—Construction—Yield—Examples —Shallow Tiibular 
Wells —Methods of Sinking—Strainers—General Method of Operating a 












CONTENTS 




PAGE 

Well-system—Arrangement and Spacing of Wells—Size of Well—Details 
of Connections —The Clogging of Wells—Tests—Yield—Examples— 
Deep and Artesian Wells —Comparison with Shallow Wells—Boring 
Deep Wells—Casing of Wells—Cost—Arrangement—Size and Spacing- 
Methods of Operation—Examples of Artesian-well Plants—Yields—Fail¬ 


ure of Wells. 2 ^° 

Horizontal Galleries and Wells— Filter-galleries—Examples—Tunnels 
in Rock—Wells and Galleries near Streams—Horizontal or Push Wells 
-Filter-cribs—Literature. 3°4 


CHAPTER XV. 

IMPOUNDING-RESERVOIRS. 

Capacity. —Use and Value of Storage—Factors to be Considered—Appro¬ 
priation of Surface-waters—Computation of Storage—Storage Calcula¬ 
tion from the Sudbury River Records—Capacity of a System of Reser¬ 
voirs.•. 3 11 

Location and Construction.— Considerations Affecting Location — Sur¬ 
veys and Preliminary Work—Depth of Reservoir—Cleaning the Site— 
Shallow Flowage—Maintenance—Literature. . 317 

CHAPTER XVI. 

EARTHEN DAMS. 

General Considerations. —The Requisites of a Dam—Kinds of Dams— 

The Dam as a Porous Structure.. 323 

The Earthen Embankment. —Advantages and Requisite Conditions— 
Forms of Construction—Stability of the Various Forms of Embank¬ 
ments—Material for Embankments—Core-walls—Embankment-slopes— 
Height above Water-line—Width of Top—Preparing the Foundation— 
Construction of the Embankment—Hydraulic Dam-construction—Slope- 
protection—Embankments and Foundations of Porous Material—Outlet- 
pipes—Gate-chambers—Valves and Sluice-gates—Waste-weirs—Care of 
Floods during Construction—Cost—Literature. 325 


CHAPTER XVII. 

MASONRY DAMS. 

The Design— General Conditions—The External Forces Acting upon a 
Dam—Internal Stresses—Conditions of Stability—Allowable Pressure— 
Weight of Masonry— A. Stability of Low Dams —Calculation of Section 
— B. Stability of High Dams —General Statement of the Problem—Weg- 
mann’s Method of Determining the Profile—Effect of Approximations 
in the Foregoing Treatment—Use of a Standard Profile—Approximate 
Triangular Profile—Forces not Considered in the Preceding Analysis— 
Top Width and Height above Water-line—Curved Dams . 









CONTENTS. 


XI 


Construction. —The Foundation—Construction of the Masonry—Impervi¬ 
ousness Earth Backing for Masonry Dams—Draw-off Arrangements— 
Masonry Waste-weirs—Other Examples of Dams—Cost—Literature. ... 

CHAPTER XVIII. 

TIMBER DAMS ; STEEL DAMS ; LOOSE-ROCK DAMS. 

Timber Dams.— Use of Timber Dams — Examples of Timber Dams . 

Steel Dams.— Combined Concrete and Steel Dams — Dams Built wholly of 

Steel... 

Loose-rock Dams. —Examples—Literature... 

B. Works for the Purification of Water. 

CHAPTER XIX. 

OBJECTS AND METHODS OF PURIFICATION. 

Purification of Water for Manufacturing Purposes—Purification of Water for 
Domestic Purposes—Outline of Methods of Purification Employed— 
Literature. 


CHAPTER XX. 

SEDIMENTATION. 

The Character of the Suspended Matter—Limitations of Artificial Sedi¬ 
mentation—Methods of Sedimentation. 

Plain Sedimentation. —Action of Subsidence—Time Required for Sub¬ 
sidence— Bacterial Efficiency of Sedimentation—Bacterial Content of 
Reservoir Sediment—Experimental Data on the Action of Finely Di¬ 
vided Matter in Water. 

Sedimentation with Coagulation. —The Use of Coagulants—The Action 
of Sulphate of Alumina—The Amount of Chemical Required—Time of 
Subsidence—Efficiency of Sedimentation with Coagulation—Action of 

Coagulants other than Sulphate of Alumina. 

Settling-basins. —Methods of Operation—Number and Size of Basins— 
Form of Basin—Arrangement of Pipes, Continuous-flow System—Ar¬ 
rangement of Pipes, Intermittent System—Drain-pipes—Clear-water 
Well—Examples of Settling-basins—Literature. . 

CHAPTER XXL 

SAND FILTRATION. 

Historical—General Description of a Sand Filter—General Results of Filtra¬ 
tion . 

Theory and Efficiency of Filtration.— Theory of Filtration—Bacteria 
in the Effluent—Efficiency of Filtration—Passage of Bacteria Confirmed 
by Disease Outbreaks—Death-rates as Measures of Efficiency. . 


PAGE 

373 

390 

392 

394 

397 

401 

403 

408 

412 

42a 

423 












Xll CONTENTS. 

Construction and Operation.—R ate of Filtration—Capacity—Number 
and Size of Beds—General Construction—Necessity of Covering Filters— 
The Filtering-sand—Friction in the Sand-layer—Thickness of Sand-bed— 
The Depth of Water on the Filter—Drainage Systems—Loss of Head in 
the Drainage System—Maximum Total Loss of Head—Inlet-pipes—Out¬ 
let-pipes and Apparatus for Regulating the Head—Automatic Regula¬ 
tion—Other Pipes and Valves—General Arrangement of Piping—Pure- 
water Reservoir—Cleaning Filters—Period of Service—Effect of Scraping 
on Efficiency of Filtration—Sand-washing—Sedimentation in Connection 
with Filtration—Bacterial Control of Filter Operations—Cost of Filters 
—Cost of Operation... 

Intermittent Filtration.—T heory of Action—Construction and Opera¬ 
tion—Double Filtration—Literature..... 

CHAPTER XXII. 

, MECHANICAL FILTRATION. 

General Description of the Mechanical Filter—Types of Mechanical Filters— 
Principles of Operation—Extent of the Use of Mechanical Filters—Ex¬ 
periments on Mechanical Filters and Results of Operation—The Louis¬ 
ville Experiments—The Cincinnati Experiments—The Pittsburg Ex¬ 
periments—Other Experiments and Tests—Efficiency as Determined by 
Typhoid Statistics—Cost—Summary—Literature. 

CHAPTER XXIII. 

MISCELLANEOUS PURIFICATION PROCESSES. 

The Fischer Tile Filter—Aeration —Softening of Water —Chemistry of 
Water-softening—The Lime Process—The Archbutt-Deeley Process— 
Softening of Water for Boiler Use—Bacterial Efficiency of the Softening 
Process—Removal of Iron from Waters—Application of Electricity to 
Water-purification—The Anderson Revolving Purifier—Domestic Filters 
—Sterilization and Distillation —Purification by the Addition of Chemi¬ 
cals —Ozone—Chlorinated Lime—Peroxide of Hydrogen—Literature... 

C. Works for the Distribution of Water. 

CHAPTER XXIV. 

PIPES FOR CONVEYING WATER. 

Materials Employed—Stresses to be Considered. 

Cast-iron Pipe.—G eneral—Thickness and Weight of Cast-iron Pipe_ 

Joints—Special Castings—Material and Method of Manufacture_Dura¬ 
bility of Cast-irou Pipe. 

Wrought-iron and Steel Pipe—A dvantages—Quality of the Material_ 

Thickness of Shell—Joints—Special Details—Coating of Steel Pipe_ 

Durability of Steel Pipe.. 


PAGE 


43i 

463 

468 


479 

497 

501 

5ii 








CONTENTS. 


Xlll 


t ■ 


Wooden Pipe. —Advantages—Bored Pipe —Stave Pipe —General Require¬ 
ments for Staves and Bands—Size of Bands—Spacing of Bands—Coup- 

ling-shoes—Specials—Leakage and Durability of Wooden Pipe. 

Other Materials Employed for Water-pipe.— Cement Pipe — Vitrified- 
clay Pipe—Materials for Service Pipes—Literature. 

CHAPTER XXV. 

CONDUITS AND PIPE-LINES. 

Classes of Conduits—Capacity of Conduits—Single or Double Conduits— 

Location of Conduits.. '.. 

Canals.— Use of Canals — Slopes and Velocities — Cross-sections — Other De¬ 
tails—Flumes. 

Masonry Aqueducts.— Advantages of Masonry Aqueducts — Size of Cross- 
section, Velocity and Slope—Materials Employed—Form and Stability 
of Section—Constructive Features—Special Details—Tunnels—Aque¬ 
ducts of Vitrified Pipe. . ... . . 

Pipe-lines.— The General Design —Material to be Employed—The Profile 
—Pressures to be Assumed—Calculation of Size of Pipe— Construction — 
Plan and Profile—Trenching—Foundations—Laying of Pipe—Testing 
and Inspection—Covering of Pipe— Appurtena?ices and Special Details 
—Provision for Expansion and Contraction—Manholes—Stop-valves— 
Air-valves—Blow-off Valves—Self-acting Shut-off Valves—Check-valves 
— Pressure-regulation Devices — Terminal Arrangements—Crossings— 

Bridges—Protection of Exposed Pipes—Submerged Pipes. 

Cost of Conduits and Pipe-lines.— Canals and Masonry Aqueducts — 
Pipe-lines—Literature. . 


CHAPTER XXVI. 

PUMPING-MACHINERY. 

Introductory—Energy Expended in Pumping Water—Work and Power Equiv¬ 
alents—Classification of Energy Losses. 

Sources of Potential Energy. —Available Sources—Fuel—Water-power.. 
Generation and Conversion of Energy.— Ordinary Efficiency of Gener¬ 
ators and Motors—The Steam-boiler—The Steam-engine—Use of Steam 
Expansively—Use of Condensers—Average Steam Consumption—Effect 

of Operating at Part Load—Heat-engines. 

The Transmission of Energy.— Methods of Transmission and General 
Efficiencies — Direct Connection — Shafting — Gearing — Belts — Rope 
Transmission —Wire-rope Transmission — Pneumatic Transmission — 

Hydraulic Transmission—Electrical Transmission.. 

The Pump in General. —Classification of Pumps— (i) Dispiace 7 ne 7 it Pumps 
—Reciprocating Pumps—The Steam-pump—Rotary Pumps—Air- and 
Steam-displacement Pumps — Continuous-flow Pumps — (2) Impeller 
Pumps —Action of Impeller Pumps—The Centrifugal Pump—Jet-pumps 
—(3) Impulse Pumps —(4) Bucket Pumps .*. 


PAGE 

5U 

527 


532 

535 

539 


547 

570 

576 

582 

533 

590 

595 















XIV 


CONTENTS. 


Pump Details.—G eneral Rules—Valves—Air-and Vacuum-chambers—Suc¬ 
tion-pipes—Location of Pumping-machinery with Respect to the Level 

of the Water Drawn From. . 

Duty and Efficiency of Pumping-machinery.—M easures of Duty—Or¬ 
dinary Duty and Efficiency of Pumping-machinery—Methods of Analyz¬ 
ing Power Losses—Capacity of Pumping-machinery—Comparison of the 
Economy of Different Designs—Examples—Literature . 

CHAPTER XXVII. 

DISTRIBUTING AND EQUALIZING RESERVOIRS. 

Office—Kinds of Reservoirs—Capacity—Location—Elevation. 

Earthen and Masonry Reservoirs.—F orm and Arrangement—Depth— 
Embankment Construction—Linings—Masonry Walls—Arrangement of 
Pipes, Valves, etc.—Covered Reservoirs—Masonry Reservoirs—Cost ... 
Stand-pipes and Tanks.—C apacity—Location— Stand-pipes —General Pro¬ 
portions— Forces and Stresses—Material Employed—Plate Thickness— 
Riveting—Bottom Details — Foundation and Anchorage — Pipes and 
Valves—Other Details—Encased Stand-pipes —Elevated Tanks —Econ¬ 
omy, Form, and Proportions—Stresses in Tank—The Tower—Connection 
of Tower and Tank—Anchorage—Inlet Pipe—Masonry Towers—Wooden 
Tanks—Storage of Water under Pressure—Literature. 

CHAPTER XXVIII. 

THE DISTRIBUTING SYSTEM. 

General Requirements—The Pressure Required—Number and Size of Fire- 
streams—Location of Hydrants—General Arrangement of the Pipe 
System—Maximum Rates of Supply for Different Areas—Velocities of 
Flow for Fire Supplies—Loss of Head in Distributing-pipes—General 
Problems Pertaining to the Flow through Compound Pipes—Calculation 
of the Pipe System—Separate Services for Different Zones of Elevation- 
Location of Pipes and Valves—Hydrants—Depth of Covering for Dis¬ 
tributing-pipes—Service Connections—Other Details—Special Fire-pro¬ 
tection Systems—Records and Maps—Literature. 

CHAPTER XXIX. 

OPERATION AND MAINTENANCE. 

Conduits and Pipe-lines—Pumping-stations—Distributing-reservoirs, Stand¬ 
pipes, and Tanks. 

The Distributing System.—M ains and Service-pipes—Valves and Hydrants 

— Detection and Prevention of Waste—Meters. 

Financial.—G eneral Considerations—Expenses and Charges to be Met_ 

Relative Cost of Different Services—Sources of Revenue—Water Rates_ 

Literature. 


PAGE 

609 

6l6 

633 

638 

653 . 


682 

716 
719 

727 












PUBLIC WATER-SUPPLIES. 


CHAPTER I. 

INTRODUCTION. 

HISTORICAL SKETCH. 

i. Water-supplies in Ancient Times —The earliest method of artifi¬ 
cially obtaining a water-supply was doubtless by the digging of wells. 
These were naturally at first mere shallow cavities scooped out of the 
ground in moist places, such as are used at the present time by savage 
tribes; but as necessity arose and the use of implements developed, 
these wells were gradually deepened. 

The digging of wells dates from a very early period. In the 
vicinity of the pyramids there still exist wells which were in use when 
those great works were constructed. Joseph’s well at Cairo is perhaps 
the most famous of all ancient wells. It is a remarkable work and 
exhibits in a high degree the skill of the people of ancient Egypt in 
matters pertaining to construction. It is excavated in solid rock to a 
depth of 297 feet and consists of two stories or lifts. The upper shaft 
is 18 by 24 feet, and 165 feet deep; the lower is 9 by 15 feet and 
reaches to a further depth of 130 feet. Water is raised in two lifts by 
means of buckets on endless chains, those for the lower level being 
operated by mules in a chamber at the bottom of the upper shaft, to 
which access is had by means of a spiral pathway winding about the 
well.* 

Frequent mention is made by the old historians of important wells 
in ancient Greece, and remains of such works are numerous in Assyria, 
Persia, and India. Probably the deepest wells were dug by the 
Chinese, depths of 1500 feet or more being reached by methods 
almost identical with those now in common use. 


* Ewbank’s Hydraulics, p. 45. 




2 


IN TROD UCTION. 


Besides the digging of wells, the ancients executed many works 
for the storage and conveyance of water. In Jerusalem underground 
cisterns were built for the storage of rain-water; and other reservoirs 
were constructed near the city to store the water which was brought 
thither in masonry conduits. Aqueducts were also built in ancient 
Greece, one mentioned by Herodotus as built to supply the city of 
Samos being still in good preservation. Some of these ancient 
aqueducts included inverted siphons of cut-stone blocks. Ruins of 
extensive underground reservoirs are to be found on the site of ancient 
Carthage, which it is believed were constructed prior to the capture 
of the city by the Romans. Works for irrigation in Egypt, Assyria, 
and India were established on an immense scale, one reservoir in 
Egypt, Lake Maeris, having had, it is said, an area of 30,000 acres. 
In the Presidency of Madras, India, the English found at the time of 
their occupation about 50,000 reservoirs for irrigation purposes, the 
construction of which had involved the building of 30,000 miles of 
earth embankment. Many of these reservoirs were doubtless of ancient 
construction. 

2. Water-works of the Romans. —Among ancient systems of water- 
supply the works of no other nation equaled those of the Romans, 
either in point of size or number; and no city in the Roman Empire 
was more abundantly supplied than the city of Rome itself. Previous 
to about 312 B.C. Rome obtained its water from the Tiber and from 
springs and wells in the immediate vicinity, but this water finally 
became so badly polluted that a purer supply was sought from distant 
sources. 

3. Aqueducts .—The conveyance of water from these new sources 
necessitated the construction of long conduits or aqueducts. These 
were often led through hills in tunnels, or carried over valleys on 
long lines of arches that are to this day the object of our wonder and 
admiration. The Romans, and indeed the Greeks, well understood 
the principle of the inverted siphon, and used it on occasion; as, for 
example, in the works of Lyons, France, where they constructed a 
siphon consisting of nine miles of lead pipe from 12 to 18 inches in 
diameter, working under a 200-foot head. The only materials, how¬ 
ever, which could be used for this purpose were stone, lead, and 
pottery, iron pipes being unknown; and the engineers of that time 
adopted what was doubtless the most economical method of crossing 
depressions, that is, by carrying the conduit on arches. 

The first aqueduct built to supply Rome was called the Aqua 
Appia, after its builder, Appius Claudius. It was constructed about 


Fig. i.—Roman Aqueducts Claudia and Anio Novus; 38-52 a.d. (Herschel.) 

(Anio Novus is built on the top of Claudia.) 















. 






























Fig. 2.—Aqueduct of Segovia in Spain. (Herschel.) 
Built about 109 A.D and still in use. 





































HISTORICAL SKETCH. 


7 


312 B.C. and had a length of about 11 miles. A second was built 
about 270 B.C. with a length of 39.5 miles, 1080 feet of which was 
supported on arches. Others were constructed from time to time until, 
with the completion of the Anio Novus about 52 A.D., there were nine 
aqueducts furnishing water to the city of Rome. These are described 
in detail by Frontinus, a Roman surveyor and water commissioner, in 
a work written A. D. 97,* in which he also gives much interesting 
information concerning the various matters coming within his official 
duties. Five more aqueducts were constructed after the time of 
Frontinus, the last dating about 305 A. D. The aggregate length of 
the fourteen was 359 miles; and aggregate length of arches, 50 miles. 
In cross-section the aqueducts of Rome varied from 3 to 8 feet in 
height by 2-J to 5 feet in width, and were built with vertical sides and 
flat or arched roofs. The interior was finished with great care to 
secure imperviousness, but in spite of this they were constantly getting 
out of repair. 

The Romans not only built works for supplying their chief city, 
but also executed many works of great importance in all parts of the 
Empire, as at Paris and Lyons in France, Metz in Germany, and 
Segovia and Seville in Spain. One-half of the aqueduct at Metz is still 
in use, although built in the year 130 A. D. That at Nimes, France, 
is famous for its great aqueduct bridge, the Pont du Gard, where three 
tiers of arches rise to a maximum height of 158 feet. 

4. Distribution System. — The distribution of water in this age was 
by no means general. In Rome the water from the aqueducts first 
passed into large cisterns, and from these was distributed through lead 
pipes to other cisterns, and to the fountains, baths, and various public 
buildings, and to private consumers. The last class was very limited 
in number, most of the people being obliged to get their supply from 
the public fountains. * Each service required a separate pipe leading 
from the distributing cistern, and the amount of water to which the 
consumer was entitled was measured by means of a short tube of speci¬ 
fied diameter. At the time of Constantine there were in Rome 11 
great thermae, 926 public baths, 1212 public fountains, and 247 
reservoirs. + 

5. Quantity of Water Supplied .—The amount of water supplied to 
ancient Rome was very liberal. It has been estimated as high as 400 
million gallons per day at the time of Frontinus, but after a careful 
study of the evidence, and allowing for the fact that usually some of 


* See reference (13), p. 14. 

f Lanciani. The Ruins and Excavations of Ancient Rome (1897), p. 56. 






8 


INTROD UCTION 


the aqueducts were out of repair, Mr. Herschel estimates the probable 
quantity delivered within the city at about 50 million gallons daily, or 
about 50 gallons per capita. Even at the latter figure the supply must 
be considered as very liberal. 

6. Quality of Water .—The ancients had some clear notions con¬ 
cerning the quality of water-supplies. In his time, Hippocrates knew 
something of the danger of drinking water which had passed through 
lead pipes, and even recommended the boiling and filtering of polluted 
water. At Rome the different aqueducts brought waters of quite 
different qualities. The best was used for domestic purposes and the 
other for baths and various public purposes, the water from one aque¬ 
duct being of such poor quality that as a rule it was used only for 
irrigation and for supplying the basin of a marine circus. In some 
cases water was passed through artificial reservoirs to purify it by 
sedimentation. 

7. The Middle Ages.—The fall of Rome brought with it the destruc¬ 
tion of the aqueducts and the general neglect of the entire subject of 
water-supply. The Popes maintained with various interruptions a. 
supply to the city of Rome, and a few other important cities were 
scantily provided with water. In other places, however, the supplies 
entirely ceased; and it is said that in some cases the inhabitants even 
forgot the use to which the old works had been put. 

The terrible ravages of pestilence during the Middle Ages were 
doubtless due in large measure to the use of grossly polluted water, 
and it was not until about the end of the sixteenth century that general 
improvement began to be made in sanitary matters. However, as 
exceptions to this there should be mentioned the construction of a few 
important works in Spain by the Moors, such as those at Cordova in 
the ninth century, and the repair of the Roman aqueduct at Seville in 
1172. 

Paris depended entirely on the river Seine for its water-supply until 
a small aqueduct was constructed in 1183, but as late as 1550 the 
supply amounted to only one quart per head per day. In London 
small quantities of spring-water were brought to the city as early as 
1235 by means of lead pipes and masonry conduits. The first pump 
was erected on the old London bridge in 1582 for the purpose of 
supplying the city through lead pipes. In Germany water-works were 
constructed as early as 1412, and pumps were introduced in Hanover in 
1527. Mention should here be made also of the aqueduct of Zempola 
in Mexico, constructed by a Franciscan monk between 1553 and 1570, 
which for two centuries ser'H to convey water from Zempola to- 


HIS TO MICA L SHE TCH. 9 

Otumba. It had a length of 27.8 miles and included three arch 
bridges of a maximum height of 124 feet.* 

8 . Development of Modern Water-works in Europe_During the 

seventeenth and eighteenth centuries progress was slow, and confined 
mainly to the cities of Paris and London. Pumps operated by water¬ 
power were erected in Paris in 1608. The aqueduct of Arcueil was 
completed in 1624 and delivered about 200,000 gallons per day, but 
at the end of the seventeenth century the supply to Paris was as yet 
only 2^ quarts per head. In London various pumps were erected on 
the bridge from time to time which drew their supply from the river 
and were operated by the current. In 1619 the New River Company 
was incorporated and laid its pipes throughout the city. It received 
its supply from the New River, and for the first time the general prin¬ 
ciple was adopted of supplying each house with water. This company 
still supplies a part of London. 

The application of steam to water-pumping in the eighteenth cen¬ 
tury gave a great impetus to the development of water-works. 
Probably the first use of steam for this purpose was in London in 1761. 
A steam-pump was also erected in Paris in 1781 and another in 1783, 
and a second in London in 1787. In all these instances the supplies 
were taken directly from the adjacent rivers. 

Since 1800 the supplies of both London and Paris have been 
greatly augmented from various sources. Some of the works are very 
noteworthy, as, for example, the two aqueducts, of respectively 81.5 
and 108 miles in length, constructed to bring spring-water to the city 
of Paris. 

In 1890 the supply of Paris was about 65 gallons per capita, of 
which about three-fourths was drawn from rivers and used for street¬ 
washing and other public purposes, while only one-fourth, or about 16 
gallons per capita, was drawn from springs and used for domestic 
purposes. The latter quantity having been found inadequate, an 
additional supply of about 30 million gallons was brought to the city 
in 1892 by means of another aqueduct 63 miles long, thus giving an 
additional supply of about 12 gallons per head. A still further addi¬ 
tion of some 1 5 million gallons has recently been provided for. 

London’s supply is now furnished by eight companies. One com¬ 
pany obtains its supply from wells in the chalk, but the others draw 
mainly from the rivers Thames and Lea. All river-water is filtered. 
In 1893 the average daily supply was 235 million gallons, 40 million 


* Eng News, 1888, xx. p. 2. 







10 


IN TROD UCTION. 


being from the chalk. The total population supplied is about 
ooo, thus giving a rate of 43 gallons per head per day. 

Notwithstanding the early existence of public water-supplies in a 
few cities, the general development of water-works was very slow in 
the first half of this century; for example, as late as 1864 there had 
been constructed in Germany but twenty-four water-works. During 
the last thirty years, however, the development in all civilized coun¬ 
tries has been very great, and the rate of growth has constantly in¬ 
creased. 

9. For many years the larger pipes were usually of wood, made 
by boring out logs to a diameter of 6 or 7 inches. Cast-iron pipes 
came into general use about 1800; and in 1820 the New River Com¬ 
pany of London replaced its wooden mains with cast-iron ones at a 
cost of $1,500,000. At one time this company had about 400 miles of 
wooden pipe in use, and often as many as ten lines of pipe were laid 
side by side to form a single main. 

When water first began to be supplied to each house it was thought 
quite impracticable to furnish a continuous supply. Instead, the water 
was turned on for only a few hours in the twenty-four, at which time 
the consumers were obliged to lay in their supply for the day. For 
sanitary reasons, and as a matter of convenience, the constant-supply 
system came into general use in spite of the many arguments against 
it. It was introduced in London in 1873, but as late as 1891, 35 per 
cent of the total supply was still on the intermittent system. 

In Europe the question of quality has received as much attention 
as that of quantity. Great expense is borne to secure, if possible, 
water from springs or mountain streams, but where this is impractica¬ 
ble, efficient purification works are established. In the early part of 
this century some use was made in Paris of artificial filters for purifying 
the water from the Seine; but filtration on a large scale was first 
inaugurated by the Chelsea Company in London, which in 1829 started 
the first large sand filter similar to those now in such extensive use. 
In the last twenty-five or thirty years the use of such filters has rapidly 
extended until now it is a rare exception to find a European city using 
unfiltered surface-water. 

10. Development of Water-works in the United States .—*Early 
Works .—The first works in America for the supply of water to towns 
were those of Boston. They were built in 1652 and served to bring 
water by gravity from springs. The first instance where machinery 
was used was at Bethlehem, Pa., the works of which were put into 
operation June 20, 1754. In this case also the water was from a 


HISTORICAL SKETCH. 


11 

spring, which is still in use as a water-supply. It was forced by a 
pump of lignum vitae of 5-inch bore through hemlock logs into a 
wooden reservoir. Eight years later the builder of these works, Hans 
Christ. Christiansen, replaced the wooden pump by three iron ones of 
4-inch bore and 1 8-inch stroke which were in use for seventeen years. 
The next works constructed were probably those at Providence, R. I., 
in 1772; and the next, those at Morristown, N. J., put into operation 
in 1791, and which still furnish water to the town. 

The first use of the steam-engine was at Philadelphia in 1800. 
These curious engines were constructed largely of wood, even the 
boiler being partly of this material. The duty was 4,790,000 foot¬ 
pounds per 100 pounds of coal.* Steam was applied to New York’s 
water-supply in 1804, these works having been inaugurated in 1799. 

In the United States, as in Europe, wooden pipes were at first used, 
but it is stated by Chanute + that cast-iron pipes were used in Phila¬ 
delphia as early as 1804, thus antedating by a few years their use in 
London. 

Besides the works above mentioned some others were constructed 
at an early date, the total number in 1800 being 16. Important steps 
in advance were made by the construction, in 1822, of the enlarged 
works at Philadelphia and, somewhat later, of the gravity works of 
New York and Boston. 

11. Progress since 1850 .—The principal development in this* 
country has taken place since 1850, and the improvements made have 
been very marked. Among these have been the perfection of cast-iron 
pipe; the improvements of pumping machinery, whereby a duty is now 
obtained greatly in excess of what was considered possible twenty-five 
years ago; the manufacture of the smaller pumps on a commercial, 
scale, thus greatly reducing the cost to small towns; the adoption of 
direct-pumping systems for small towns, thus also in many cases greatly 
reducing first cost; and the development of the ground and artesian 
water-supplies in the Western States. The public water-supply has 
now come to be so much of a necessity that it is rare to find a village 
of 2000 inhabitants without its public supply. 

The growth in the number of water-works since T850 is shown by 
the following table taken from the “Manual of American Water¬ 
works ” for 1891 and 1897. It gives the total number of water-works 
in existence at the end of various years, and the number built in each 
period. 


* Illustrated description in En«. News, 1887, xvu. p. 247. 
f Trans. Am. Soc. C. E.. 18S0, ix. p. 220. 



12 


IN TROD UCTION. 


Year. 

Number of 
Works. 

Number of 
Works Built 
in each 
Period. 

Year. 

Number of 
Works. 

Number of 
Works Built 
in each 
Period. 

1850 

83 


1875 

422 

179 

1855 

106 

23 

1880 

598 

176 

i860 

136 

30 

1885 

IOI3 

415 

1865 

162 

26 

1890 

1878 

865 

1870 

2 43 

8l 

1896 

3196 

1318 


The new works built between 1890 and 1896 were of course mainly 
for small towns, but a large amount of work has also been done each 
year in increasing the supplies for the larger cities. In 1880 the total 
population supplied was 11,809,231, while in 1890 it was 22,814,061, 
nearly one-half of the increase being due to the increase in population 
of cities already supplied in 1880. The total estimated cost of the 
works up to 1891 was $543,000,000; number of miles of mains 32,400, 
taps 2,213,000, and hydrants 220,000. 

12. Present Conditions and Necessities .—As regards the improve¬ 
ment in the quality of water supplied not so much progress has been 
made as in increasing the quantity, and in this respect this country is 
far behind Europe. A large proportion of our largest cities use water 
taken directly from streams more or less polluted by sewage, and as 
yet little has been done to improve these conditions. The problem 
here is rendered especially difficult by reason of the enormous quanti¬ 
ties of water used by American cities as compared with those of other 
countries. 

From this statement of present conditions it is evident that the 
engineering work of the future lies principally in the development of 
new and better sources of supply, in providing increased quantities for 
our rapidly growing cities, and especially in the improvement of the 
quality of existing supplies. In the management of water-works, also, 
much needs to be done in the direction of waste prevention, both to 
reduce the immediate cost of operation and in many places to render it 
possible to install purification works at a reasonable expense. 

VALUE AND IMPORTANCE OF A PUBLIC WATER-SUPPLY. 

13. Domestic Use.—The most important use of a public water¬ 
-supply is that of furnishing a suitable water for domestic purposes. 

The absolute necessity of a supply of some sort for such purposes in a 
large city is well appreciated, but the value of purity is, by many, not 
rated as high as it should be. The transmission of certain diseases 

















VALUE AND IMPORTANCE OF A PUBLIC WATER-SUPPLY . 13 

such as cholera and typhoid fever by polluted water is now universally 
recognized, and the value to a city of a pure supply when compared to 
one constantly polluted by sewage can scarcely be overestimated. 
Many examples of the benefits arising from the introduction of new or 
improved supplies are given in Chapter X. 

A public supply of pure water is of great value not only in large 
cities, but in the smaller towns and villages. Too often a supply for a 
village is designed with almost exclusive reference to fire-protection, 
and little attention is paid to the quality of the water, the people 
expecting to depend on wells as before. As a rule, however, a good 
pure water is quite as much to be desired in this case as for a city 
supply, and, if provided, will in many cases be quite as fully utilized. 

Another highly important function of a water-supply is that of 
furnishing the necessary flushing-water for a sanitary system of 
drainage. The most satisfactory and economical method yet found 
for disposing of the organic wastes of a community is by the water- 
carriage system. Such a sewerage system is manifestly of but slight 
value to the public at large without the coexistence of a public water- 
supply, as otherwise the necessary water for the flushing of closets — 
the most important function of a sewerage system—can be afforded 
by but few. 

Besides furnishing an improved supply from the sanitary stand¬ 
point, a public works may often be made to furnish a water which for 
other reasons will be of greatly increased value to the domestic 
consumer; such as a soft water in place of a hard well-water—a point 
of very considerable importance to both domestic and commercial 
users. 

14. Commercial Uses. —The commercial value of a good water- 
supply is appreciated when one considers the large number of manu¬ 
facturing interests which require for their operation large quantities of 
suitable water. Such establishments as sugar-refineries, starch- 
factories, bleaching and dyeing houses, breweries, chemical works, and 
various other factories require an abundant water-supply, and in some 
cases a water of a high degree of purity. The question of water-supply 
indeed often determines the location of such factories. Large quanti¬ 
ties are also used for operating elevators, for boiler purposes, and for 
many other uses that may be classed as commercial. 

15. Public Uses. —The most important public use of a water-supply 
is perhaps in extinguishing fires. The economic value of a good fire- 
protection system is directly shown in the reduced rates of insurance 
which follow its introduction or improvement. Instead of distributing 


H 


INTROD UCTION. 


a heavy fire-loss among the people of a community through high rates 
of insurance it is assuredly much better economy to contribute to the 
maintenance of a public water-works, which at the same time provides 
a suitable water for other purposes. To permit of the establishment of 
certain classes of factories it is absolutely essential that an efficient fire- 
protection be furnished. 

Other important public uses of a water-supply are in street-sprink¬ 
ling and sewer-flushing, in furnishing water for public buildings, and 
for drinking and ornamental fountains. A real value exists in the 
improved appearance which may be given a city by the use of water in 
fountains and for lawns and public parks; and indeed all the benefits 
accruing from a good water-supply act indirectly to increase the 
desirability of a town for many purposes and to enhance the value of 
the property therein. 

LITERATURE. 

1. Ewbank. Hydraulic and other Machines for Raising Water. New 

York, 1876. 

2. d’Avigdor. Water-works, Ancient and Modern. Engineering , 1876, 

xxi. p. 403. 

3. Grahn. Statistik der stadtischen Wasserversorgung. Munich, 1878. 

4. Chanute. Annual Address. Trans. Am. Soc. C. E., 1880, ix. p. 217. 

5. Higgins. The Old Water-supply of Seville. Proc. Inst. C. E., lxxviii. 

P- 334 - 

6. Early American Pumping and Distributing Plant. Eng. News , 1887, 

xvii. p. 247. 

7. The Aqueduct of Zempola, Mexico. Eng. Nezvs , 1888, xx. p. 2. 

8. Manual of American Water-works. New York, 1891. 

9. Croes. The Water-works of Carthage. Eng. Record , 1891, xxv. p. 8. 

10. Evolution of Water-supplies. Eng. Record, 1896, xxxiv. p. 162. 

11. Lanciani. The Ruins and Excavations of Ancient Rome. Boston 

1897. 

12. Wegmann. The Water-works of Laodicea, Asia Minor. Eng. Record, 

1899, xl. p. 354. 

13. Herschel. Frontinus, and the Water-supply of Rome. Boston, 1899. 

A translation of Frontinus, with many valuable comments on the 
water-supply of Rome. 


/ 


PART I. 

REQUIREMENTS AND RESOURCES. 

A. QUANTITY OF WATER REQUIRED: SOURCES OF SUPPLY. 


CHAPTER II. 

QUANTITY OF WATER REQUIRED. 

16. Nature of the Problem. — One of the first questions to be 
answered when a new or enlarged water-supply is under consideration 
is that relating to the quantity which will be required when the works 
are completed, and for a certain period in the future. In the nature of 
the case this problem can be solved only approximately. Since the 
total quantity consumed is sure to increase in the future, the chief effect 
of an error in the estimate will be to vary the date at which an enlarge¬ 
ment of the capacity will be required; but even so, to secure the most 
economical construction it is necessary that as close an estimate be 
made as possible. 

In estimating consumption there will arise two cases: 

(1) The case of a town being supplied for the first time; 

(2) The case of an enlargement of an old supply. 

In the first case an estimate of the immediate future consumption 
must be made by a study of the consumption of towns of similar 
characteristics, taking into consideration the various modifying influ¬ 
ences. In the second case the consumption is already known, and that 
for a few years in the future can be readily estimated. In both cases, 
estimates for long periods ahead, such as twenty or thirty years, are 
very uncertain. To be of any value they must be based upon a careful 
study of the circumstances affecting increase in population and the 
use of water. 


15 






1 6 QUANTITY OF WATER REQUIRED . 

Estimates of consumption should include not only the average 
quantity which will be required, but also the variation in the consump¬ 
tion, in order that the various parts of the works—the reservoirs, 
pumps, and distributing system—may be properly proportioned. 

17. Consumption, How Stated.—Consumption is usually stated in 
terms of the average daily consumption per capita throughout the year 
on the basis of the total population of the town or city. In large cities 
the total population corresponds nearly to the number of consumers, 
but in small towns and villages only a small percentage of the inhabi¬ 
tants may be users, and the statistics for such places are of little value 
unless the number of takers or taps is also given. 

The amount consumed is determined in various ways. Where 
pumps are used it is obtained by multiplying the number of strokes 
made by the pumps by the displacement of the plungers, no allowance 
ordinarily being made for slip. The resulting error will not usually 
exceed 2 or 3 per cent, and is not of great consequence in this connec¬ 
tion, but occasionally, as in the case of leaky suction-mains or well- 
tubes, large quantities of air are pumped and the “ slip ” becomes very 
great. In gravity works, the water is more or less accurately measured 
by weirs, or by the known capacity of certain pipes or conduits, or is 
merely guessed at. 

In whatever way determined, the total amount is stated as the 
consumption. It therefore includes all water supplied, whether used, 
or wasted, or lost through broken pipes or mains. Sometimes, also, it 
includes water used in the condenser of the pumping-engine, but this 
should obviously be deducted. 

18. Influences Affecting the Consumption per Capita.—One of these 
influences is the number of inhabitants in the town or city. This 
element affects the per capita consumption chiefly by affecting the 
extent to which use is made of private sources of supply. Thus in 
large cities the use of the public supply is almost a necessity, while in 
small towns and villages the private supplies may remain in use to a 
large extent long after the introduction of the public supply. 

The nature of the industries of a town is a large factor in determin¬ 
ing the amount of water used; also the wealth and habits of the people, 
nnd the extent to which water is used for fountains, watering of lawns, 
street-sprinkling, and other public purposes. Climate has also a very 
considerable influence, especially as to the amount used for sprinkling 
purposes and that which is wasted in winter to prevent freezing. It is 
probable, however, that the most important factors in determining the 
consumption is the degree of care taken to detect leakage or waste, 


CONSUMPTION FOR FA PIOUS PURPOSES. 


17 


and the fact as to whether the water is sold by measure or otherwise. 
Good quality, abundant quantity, and high pressure tend to increase 
the consumption by encouraging a more liberal use and often, at the 
same time, greater wastefulness. 

In many cases the introduction of a new or an improved water- 
supply is followed by such an increase in consumption that the time 
comes sooner than expected when the new works are no longer 
adequate to supply the demand. When estimating the probable con¬ 
sumption under the second case, i.e., the enlargement of an old 
supply, it is necessary then that the figures relating to the old works 
be used with considerable caution. Important changes in the character 
of a city sometimes also occur, and with small towns such changes may 
take place very rapidly. These, however, can scarcely be predicted. 

19. Consumption of Water for Various Purposes.—In order to make 
an intelligent application of data pertaining to the use of water, some 
knowledge is desirable of the consumption for various purposes. This 
information is especially useful in the design of works for places of 
peculiar characteristics, in the design of the different parts of a dis¬ 
tributing system, and of separate supplies for different purposes. 
Unfortunately but little accurate information relating to the consump¬ 
tion of water for different purposes is to be had, as the use of meters 
for all consumers is of rare occurrence. 

The different uses of water may conveniently be divided into four 
general classes: (1) Domestic use; (2) Commercial use; (3) Public 
use; (4) Loss and waste. 

Probably the best analysis yet made of the subject of water-con¬ 
sumption for different purposes is that by Brackett,* and in the 
following discussion his paper has been freely drawn upon; other data 
are taken from various city reports. 

20. Domestic Use .—The following table, mainly from Brackett, 
gives a good notion of the actual quantities used for domestic purposes 
and the variation in the consumption due to differences in the character 
of the population. The figures are from metered supplies and represent 
what may be considered as legitimate consumption, even though con¬ 
siderable water may have been wasted. 

The consumption per capita is seen to vary from 6.6 to 59 gallons 
per day for the lowest and highest class of dwellings respectively; and 
the average for a town varies from 11.2 gallons for Fall River, a 
manufacturing city, to 44. 3 gallons for Brookline, a wealthy suburb of 


* Trans. Am. Soc. C. E., 1895, xxxiv. p. 1S5. 






QUANTITY OF WATER REQUIRED. 


18 

Boston. From these data it would appear that for a metered supply 
the domestic use may easily vary from i 5 to 40 gallons, but that an 
allowance of 20 to 30 gallons would in most cases be abundant. 

TABLE No. 1 . 

CONSUMPTION PER CAPITA FOR DOMESTIC PURPOSES AS DETERMINED BY METER 

MEASUREMENTS. 


City. 

Numberof 

Persons. 

Consump¬ 
tion per 
Capita in 
Gallons. 

Remarks. 

Boston, Mass. 

1,461 

59 

Highest-cost apartment-houses in city. 

4 4 4 4 

8,432 

32 

Moderate-class apartment-houses. 

4 4 4 4 

1,844 

16.6 

Poorest-class apartment-houses. 

4 4 4 4 

1,699 

46.1 

Boarding-houses. 

Brookline, Mass.. 

4,140 

44-3 

Average of all dwellings supplied by meter. 

Newton, Mass.... 

2,450 

26.5 

All houses supplied with modern plumbing. 

4 4 4 4 

3,005 

6.6 

These families have but one faucet each. 

Fall River, Mass.. 

170 

25.5 

The most expensive houses in the city. 

« 4 *4 4 4 

70,000 

11.2 

Average of all. 

Worcester, Mass.. 

90,942 

16.8 

Whole domestic consumption. 

4 4 4 4 

187 

23-4 

Cedar Street, best class of houses. 

4 4 4 4 

809 

156 

Austin Street, cheaper houses. 

London, Eng. 

8,183 

25-5 

Houses renting from $250 to $600 each, having 
bath and two water-closets. 

4 4 4 4 

5,089 

18.6 

Middle class, average rental $200. 

Yonkers, N. Y.... 

34,000 

20.6 

Average of all. 

Madison, Wis. 

13,000 

21.3 

Total domestic and commercial use. 


With an unmetered supply the domestic consumption and waste 
may be many times greater than the figures given above. In Boston 
the estimated actual domestic consumption, including waste, was in 
1892 (for the Cochituate works) 62.24 gallons per capita out of a 
total of 94.93 gallons. In Philadelphia, a city having an unmetered 
service, meters were placed experimentally upon the services of twenty 
residences in different parts of the city. The consumption for four 
of these services averaged 149 gallons per head per day, the highest 
rate being 181 gallons. In several other cases the rate averaged from 
40 to 60 gallons, while in some it was as low as 9 gallons. In 1893, 
142 houses were inspected and the average consumption found to be 
222 gallons per capita. 

21. Commercial Use. —Under this head are included all uses for 
mechanical, trade, and manufacturing purposes. Large users of water 
for such purposes are office buildings and stores, hotels, factories, 
elevators, railroads, breweries, sugar-refineries, and a few other indus¬ 
tries. In 1892 the consumption in Boston for various commercial 
purposes as determined mostly by meters was as follows: 




















CONSUMPTION FOR FA RIO US PURPOSES. 


19 


Office-buildings and stores, 

gals, per head for total population... 

... II. 17 

Steam-railroads, 

ii 4 4 

i i 

4 4 

4 4 4 4 


Sugar-refineries, 

4 4 4 4 

i i 

4 4 

4 4 4 4 


Factories, 

4 4 ii 

i i 

4 4 

4 4 4 4 

2.15 

Breweries, 

ii 44 

< 4 

4 4 

4 4 |« 


Steamers and shipping, 

ii ii 

4 4 

4 4 

4 4 « 4 


Elevators and motors, 

a a 

4 4 

4 4 

4 4 4 4 


Saloons, 

a a 

4 4 

4 4 

l< 4 4 


Hotels, 

a a 

4 4 

4 4 

<4 4 4 


Miscellaneous, 

a a 

4 4 

< 6 

4 4 4 1 


Total 

a a 

4 4 

4 4 

4 4 4 4 



Similar statistics for 1880 indicated a consumption of about 25 
gallons per capita. At Syracuse, N. Y., in 1888-89, 7 * 2 gallons per 
capita were used in operating elevators and 23.2 gallons for other com¬ 
mercial purposes. In New York City the consumption for commercial 
purposes is about 24 gallons per capita. Mr. Brackett considers that 
35 gallons per capita should be allowed in making provision for the 
future supply of Boston. 

In smaller cities the consumption for commercial purposes would 
in many cases be much less, while in some it might be more. In 
Fall River, for example, in 1892 the commercial consumption was 
estimated at 2 gallons per capita, this low value being due to the fact 
that most of the factories at that place get their supply directly from 
the river. In Yonkers, N. Y., a fully metered town (population 
34,000), the consumption for commercial purposes was, in 1897, 27.4 
gallons per capita, the total being 102 gallons. Considering the 
above data, it is probably fair to estimate the consumption for com¬ 
mercial purposes at from 5 to 35 gallons per capita according to the 
nature of the town. 

22. Public Use. —This includes the water used for schools and 
other public buildings, street-sprinkling, water-troughs and fountains, 
sewer-flushing and the flushing of water-mains, fire-extinguishment, 
and a few other occasional uses. Water for such purposes is seldom 
measured, but the amount is not likely to exceed on the average a few 
gallons per capita, although the rate of consumption is far from being 
uniform. In the following table is given the consumption for various 
public purposes in Boston for 1892, and in Fall River for 1899, the 
water being in both cases partly metered and partly estimated. 


Boston. 

Public buildings, schools, etc., gals, per capita. 2.30 

Fall River. 
1.36 

Street-sprinkling, “ 

'4 

“ . 1.00 

1.02 

Sewer-flushing, “ 

44 

“ . 10 

.48 

Water-troughs and fountains, “ 

44 

“ . 25 

1.91 

Fires, “ 

44 

“ . 10 

.11 

Blowing off dead ends, 

44 

4 4 

• •*••••• ••• 

•33 

Miscellaneous, “ 

4 4 

4« 

• *•••••• ••• 

•36 

Total, “ 

4 4 

“ . 3-75 

5-57 








































20 


QUANTITY OF WATER REQUIRED. 


In many places much more water is used for sprinkling purposes 
than the quantities given above. Estimates for a few places are as 
follows: In Minneapolis, in 1897, 5 gallons per capita; in Indianapolis, 

3 gallons; Rochester, N. Y., 3 gallons; Newton, Mass., 4 gallons; 
Madison, Wis., 10 gallons. Street-sprinkling is carried on for about 
half the year only, so that the actual rate of consumption is about 
double these figures. Lawn-sprinkling in public parks would add very 
little. Assuming an amount for this purpose equal to inch in depth 
per day, and allowing 10 acres for each 25,000 inhabitants, the average 
used would be equal to about 1 gallon per head per day for the period 
of two or three dry months. 

For fire purposes the average consumption is very small, but at 
times the rate is very high. (See Art. 32.) 

Few American cities use any considerable quantity of water for 
ornamental purposes, and it might be well to consider whether a part 
of the large amounts wasted in some of our cities might not be more 
advantageously used in adding to the attractiveness of public parks and 
squares by means of ornamental and drinking fountains. The amount 
of water used in some of the ornamental fountains in the European 
capitals is at times very large, but does not add greatly to the average 
consumption. In Paris the average is estimated at only about 2.4 
gallons per capita daily, although there are many fountains using from 

4 to 100 gallons per second. These, however, are-allowed to play 
only at certain hours or on special occasions. 

The total consumption for public purposes may finally be estimated 
at from 3 to 10 gallons per head, averaging perhaps 5 gallons, the 
amount depending largely on the item of street-sprinkling. 

23. Loss and Waste .—The enormous quantities of water (150 to 
300 gallons per head per day) used by some of the large cities of the 
United States, when compared with the foregoing data from metered 
supplies, indicate that a very large percentage of the water furnished is 
lost through leakage or is wasted by the consumer. The chief causes- 
of such waste are bad plumbing, leaky mains, waste to prevent freez¬ 
ing, and willful or careless waste. The waste by the domestic con¬ 
sumer has already been considered under domestic consumption. With 
metered supplies, water may still be badly wasted by the consumer, 
but such being paid for at regular rates, it must be considered as legiti¬ 
mate consumption. But when all services are metered and a liberal 
allowance is made for public uses, there is still a large amount of water 
apparently furnished which is not accounted for. 

This discrepancy or loss is due to three causes: errors in meters. 


CONSUMPTION FOR VARIOUS PURPOSES. 


21 


errors in estimating the pumpage due to the slip of the pumps, and 
actual loss through leaks and breakages. Meters, when old, will tend 
to register less than the true amount, especially when measuring small 
quantities; furthermore, the actual amount pumped is nearly always 
less than that figured from plunger displacement, and to correct this 
error an insufficient allowance, or no allowance at all, may be made. 
Both these errors act to increase the apparent loss. Probably their 
combined effect will rarely be less than 5 per cent of the total amount 
pumped, and may easily reach 10 per cent. The actual loss is, there^ 
fore, often considerably less than the apparent loss. 

Below are given data for several metered towns showing the 
amounts ‘‘unaccounted for,” including, in most cases, water used for 
public purposes: 




Amount Unaccounted for. 

City. 

Year. 

Per cent of 
Total. 

Gallons per 
Capita. 

Yonkers, N. Y. *. 

1897 

51 

52 

Newton, Mass. *. 

1892 

47 

28 

Milton, Mass. * . 

1893 

50 

27 

Fall River, Mass.f. 

1899 

24.4 

8.8 


1893 

30 

10 

Hackensack Water Company, N. J.* 

High-service district. 

Englewood “ . 

Ridgefield “ . 

* 1883-8 
1888 
1885-8 
1S97 

27 to 64 
44 to 60 

2 tO 58 
65 ' 

29 


* Public use included. 

f Five per cent allowed for under-registration of meters. 
\ Five per cent allowed for slip of pumps. 


On account of the unknown quantity used for public purposes in 
many of the above places, and the possible errors of registration, no 
definite conclusions can be drawn as to the actual loss in each case. 
But after making liberal allowance for public use, the data show the 
existence of large discrepancies between supply and consumption that 
must be taken account of. Brackett estimates 1 5 gallons per capita as 
the minimum allowance for this item where meters are used, and it is 
apparent* from the above table that it may considerably exceed this 
amount. 

24. Leakage from mains has been directly determined in several 
cases. Tests of comparatively new pipe systems indicate a leakage of 
from 500 to 1200 gallons per day per mile, and one engineer specifies 
a maximum allowable leakage of 60 to 80 gallons per mile per inch 






















22 


QUANTITY OF WATER REQUIRED. 


of diameter of pipe.* * * § Certain tests of pipes in several German and 
Dutch cities showed leakages of less than 300 gallons per mile.t A 
test of a 24-inch main by Mr. Brush J showed a leakage of 6400 gallons 
per day per mile, under a pressure of 110 pounds per square inch. In 
large systems, cases of breakages of 4- and 6-inch mains have occurred 
which have remained long undiscovered, the water flowing away 
through adjacent sewers at rates as high as 100,000 gallons per 24 
hours. In a small system such breaks would be immediately indicated 
by a reduction of pressure at the pumps. 

Pipe-leakage is likely to increase as the system gets older, on 
account of the loosening of joints through settlement, increased leakage 
of valves, etc. As a general estimate Mr. Kuichling§ uses the values 
of 2500 to 3000 gallons per mile of pipe. This is equivalent to from 
3 to 10 gallons per capita, the population per mile of pipe usually 
ranging from about 300 to 1000. 

Considering these various facts, the total amount of water lost or 
unaccounted for in metered supplies may be placed at from 15 to 30 
gallons per capita. 

25. Total Consumption per Capita.—Recapitulating the above esti¬ 
mates for various purposes, we have, as reasonable extreme and average 
values for those supplies having a fairly good meter system: 


Use. 

Gallons per Capita. 

Daily. 

Minimum. 

Maximum. 

Average. 

Domestic. 

15 

40 

25 

Commercial. 

5 

35 

20 

Public. 

3 

10 

5 

Loss. 

15 

30 

25 

Total.. 

38 

ii5 

75 


As it will seldom occur that for any given place the conditions are all 
favorable for a minimum or a maximum use for all purposes, the above 
totals are to be considered as much more extreme figures than the 
separate items. 


* Trans. Am. Soc. C. E., 1897, xxxvm. p. 30. 

f Jour. f. Gasbel. u. Wasservers ., 1894, p. 722. 

+ Trans. Am. Soc. C. E., 1888, ix. p. 89. 

§ Trans. Am. Soc. C. E., 1897, xxxvm. p. 19. 




























TOTAL CONSUMPTION- PER CAPITA 


23 


26 In Table No. 2 is given the total per-capita consumption for 
many American cities for the years 1890 and 1895. For the former 
year the data are from the Manual of American Water-works for 
1890-91, and for the latter they have been compiled chiefly from the 

TABLE NO. 2 . 

CONSUMPTION OF WATER IN AMERICAN CITIES AND TOWNS IN 1S9O AND 1895. 


City. 


New York. 

Chicago .. 

Philadelphia. 

Brooklyn. 

St. Louis. 

Boston. 

Cincinnati. 

San Francisco... 

Cleveland. 

Buffalo . '.. 

New Orleans. 

Washington... 

Montreal. 

Detroit . 

Milwaukee .. 

Toronto. 

Minneapolis. 

Louisville.. 

Rochester. 

St. Paul . 

Providence . 

Indianapolis. 

Allegheny. 

Columbus. 

Worcester. 

Toledo ...... 

Lowell. 

Nashville . 

Fall River. 

Atlanta. 

Memphis. 

B uebec. . 

ayton, O.. 

Camden, N. J. 

Des Moines. Ia.. 

Hamilton, Ont. 

Ottawa, Ont.. 

Yonkers, N. Y. 

Newton, Mass. 

Aurora, Ill. . 

Madison, Wis... . 

Muscatine, la. 

Ashland, Wis. ; . 

Champaign and Urbana, Ill 
South Framingham, Mass.. 

Chippewa Falls, Wis. 

Melrose, Mass. 

Beloit, Wis. 

Conneaut, O.. 

Foxborough, Mass. 

Clinton. Ill . 

De Kalb. Ill. 

Shenandoah,Ia. 


Population, 

1890. 

M 

3 ? Population per Tap. 

00 Per cent of Taps 

'0 Metered. 

co Consumption per 

'o Inhabitant Daily. 

00 Per cent of Taps 

$ Metered. 

Is 

- X 

G. 4 -* 

3 2 

cr . — 

c s 

C 

u 

1895-. 

1,515.301 

13,9 

20.2 

79 

27.0 : 

100 

1,099,850 

7 * 1 

2.5 

140 

2.8 

*39 

1,046,964 

6.1 

0.3 

132 

0.74 

163 

838,547 

8.7 

2-5 

72 

19 

8q 

45 L 77 o 

11.8 

8.2 

72 

7-4 

98 

448,477 

.6.6 

5 -o 

80 

5-2 

IOO 

305,891 

8.5 

4 -i 

112 

6-5 

*35 

298,997 

0.9 

41.4 

6l 

28.0 

63 

270.055 

8.7 

5-8 

103 

4-5 

142 

255.664 

6.3 

0.2 

186 

0 83 

271 

242,039 

54 -o 

O.4 

37 


35 

230,392 

6-5 

0.3 

158 

i -5 

200 

216,000 

5-3 

i -7 

67 

i .6 

83 

205,876 

5 -i 

2.1 

l6l 

8.2 

152 

204.468 

11.1 

3 1 -9 

1 IO 

51.0 

lOf 

181,000 

4.0 

4.1 

IOO 

3-7 

TOO 

164,738 

16.5 

6-3 

75 

16.0 

8s 

161,129 

11.9 

5-9 

74 

6.6 

97 

133.896 

5-4 

11 4 

66 

18.0 

7 i 

133 .156 

12.7 

4.2 

60 

i -7 

60 

132,146 

9.4 

62.4 

48 

74.0 

57 

105.436 

35 6 

7.6 

71 

7 -i 

74 

105.287 

7.0 

O 

238 

7 • 1 

247 

88,150 

H -5 

6.4 

78 

9-3 

127 

84,655 

8.9 

8y • 4 

59 

90.0 

66 

81.434 

18.6 

9.4 

72 

35 0 

70 

77,696 

9.2 

22.9 

66 

33 -o 

82 

76.168 

14.9 

0.8 

146 

24.0 

139 

74,398 

14.9 

74.6 

29 

82.0 

35 

65,533 

20.0 

89 6 

36 

99.0 

42 

64.495 

II .9 

3-7 

124 

4.6 

IOO 

63,000 

IO.4 

O 

160 

O 

170 

61,220 

20.0 

3 - 8 

47 

24.0 

50 

58,313 



131 

O 

200 

50,093 

20.0 

60.0 

55 

42.6 

43 

48,000 

2.0 

0 

78 

0.2 

•3® 

44,000 

4.2 

O 

130 

O 

200 

32,033 

12.0 

82.4 

68 

99 8 

IOO 

24,379 

5-5 

67-4 

40 

77-3 

65 

19.688 

8.2* 

19 3 

40.7 

36.0 

56 

13,426 

11.0 

31.0 

. 40 

61.0 

5* 

11,454 

26.3* 

7-5 

35 

14.0 

38 

9,956 

9 9 * 

2.8 

90 

7-7 

108 

9 , 35 ° 

7 - 3 * 

2-5 

43 

21 

74 

9,239 

* 3 -o 

15.0 

22 

23 

38 

8,670 

7.4* 

6.6 

I 3«8 

2-3 

108 

8,519 

4 - 2 . 

0 


1-7 

7 * 


10,2* 





3.241 

5 - 2 * 



4.1 

W t 

97 

2,933 

8.9* 



34 -o 

44 

2,598 

4. I* 

3 -o 

27.0 

I . I 

99 

2,579 

5 - 6 * 

• • • • . • 

26.3 

9.1 

37 

2,440 

i 5 - 5 * 



15-5 

39 























































































24 


QUANTITY OF WATER REQUIRED. 


Manual for 1897 in connection with estimates of population from various 
sources. In addition there are given the population for 1890, and the 
population per tap and the percentage of taps metered for both 1890 
and 1895. 

For cities above 25,000 inhabitants the size has no apparent relation 
to the consumption. This fact is more clearly shown by the average 
consumptions for groups of cities of different size. Mr. Kuichling* 
finds for 100 of the largest cities in the United States and Canada the 
following averages for 1895 : 

For Cities of a Population of Consumption per Capita, 

1,000,000 and more. 106 gallons. 

600,000 to 300,000. 122 “ 

300,000 to 100,000. 106 “ 

100,000 to 50,000. 105 “ 

50,000 to 30,000. 105 “ 

The large value for the second group is due to the high consumption 
of 220 gallons for Pittsburg. For towns smaller than the above the 
consumption is generally lower, partly on account of a less commercial 
use and partly because the water is used by only a portion of the com¬ 
munity. The very considerable increase in consumption in many of 
the smaller towns from 1890 to 1895 as shown in the table is largely 
due to an increase in the number of takers. 

In a general way the effect upon consumption of the ratio of popu¬ 
lation to taps is observable for the various cities, but too many other 
elements enter to enable any definite relation to be traced. The great 
irregularity in consumption among the large cities, and the enormous 
quantities used by some, can be explained only on the supposition that 
a large part of the water is wasted and lost. The effectiveness of 
meters in preventing very high rates of consumption is clearly brought 
out by the table; for with one exception, no city having 10 per cent 
of its taps metered has a consumption appreciably above 100 gallons. 
There are some cities with few meters that have not a high consump¬ 
tion, a result brought about usually by a very thorough system of 
inspection. 

The average consumption for cities of more than 25,000 inhabit¬ 
ants, and with 10 per cent of the taps metered, is about 75 gallons, 
with 139 gallons as an extreme value; and for the small places about 
50 gallons, with 75 as a maximum. These values correspond very 
well with the previous detailed estimate. 

27. Increase in Consumption.— For many years past there has been 
a large and steady increase in the consumption of water. This is due 


* 1 rans. Assn. C. E. of Cornell University, 1898, p. 10 












INCREASE IN CONSUMPTION . 


25 


chiefly to the more general use of water and to an increase in the 
number of fixtures in the houses supplied; but where no restriction has 
been imposed upon the use of water the waste has increased even faster 
than the legitimate use, so that in many cases the consumption has 
become enormously high. 

I o exhibit the general tendency the consumptions per capita for 
several large cities for the period from 1875 to 1895-98 have been 
plotted in big. 3. I he steeper portions of the curves for the cities of 


200 


/so 


$ 

* 


ZOO ‘ 


I 

§ 

0 so 






/ 

t 









t 










1 

1 








y 


y 








£ 










y 



\ 









4 

\, 








■jug 

f 

V 








y fp < - 





i\/ 



** 

. ^ / 


yv 





$/ 

iy 

/ 

J 

/ 


AJ ’ 

i/ 


\ 

\ 



A/ 

N - 1 / 

ioty; 



\ <i 



\ ■" 

\ 

> 



ww, 

W'/si* 


; 

.S. 





— 




( m . - 

—! 



/ v 







/ c 

Zasqow 








* 

-/- ' 


,'Nencz 

/ 



yy... 

. 

* 


% 

r 

■ rr^i 

J? — 







































200 


/SO 


too 


£ 

k> 

V 

5 


50 o 


/ 87 S 20 QS 


30 


/S 7 S 


J so 


30 


Fig. 3. —Variation in Yearly Rates of Consumption. 

Ciit Jnnati, Philadelphia, and Detroit show in what manner the 
iinrr itricted use of water is likely to raise the consumption. Omitting 
such cases of excessive rates of increase, there still remains a marked 
tendency towards an increased consumption of water. With originally 
low rates of consumption this increase is large even with well-metered 
cities, such as Lowell with 33 per cent of the taps metered, Providence 
with 74 per cent metered, and New York with 27 per cent metered. 
Milwaukee with 32 per cent metered in 1890, and 51 per cent metered 
in 1895, shows some decrease. Some of the cities, such as Boston and 
St. Louis, have good systems of inspection, and the consumption, 
though not high, is yet increasing at quite a high rate. 

It would therefore appear that even with the best systems the per- 
capita consumption of water is likely to continue to increase for some 
time to come. In case the use of water is already restricted, it would 


















































26 


QUANTITY OF WATER REQUIRED. 


not in general be safe to estimate the amount of this increase at less 
than io or 15 gallons for the next decade. Where few meters are used 
at present, the consumption could in many cases be greatly reduced by 
their introduction, or by a better inspection system. The result of the 
introduction of meters in Detroit, begun in 1886, is very marked. 

The difficulty of estimating future consumption is illustrated by the 
case of Boston. In the investigation for the Metropolitan district, 
made in 1894, it was estimated that 100 gallons per capita would be 
sufficient for thirty years to come. As a matter of fact the consump¬ 
tion in the district increased from 83 gallons in 1893 to 94 gallons in 
1897, a rate of increase which if maintained for a few years would carry 
the consumption far beyond the estimated amount. 

28. Variations in Consumption.—The foregoing articles have dis¬ 
cussed only the average consumption throughout the year. There will 
now be considered the variations which occur in the consumption from 
time to time. 

For the design of the different parts of the works it is desirable to 
know the monthly, the daily, and the hourly variations. The varia¬ 
tions for periods of one month or more are of use in questions pertaining 
to large storage-reservoirs, while those for short periods of a few days 
or hours are of use in the design of pumps, service-reservoirs, and 
mains. For example, if no storage exists between the pumps and the 
consumer, then the pumps must be designed to furnish water at the 
maximum possible rate of consumption, while with a certain amount 
of storage they may be designed with only sufficient capacity to supply 
water at the maximum daily rate or at the maximum weekly rate. 
Likewise with no storage the source of supply, whether surface-water 
or ground-water, must have a capacity sufficient at all times to supply 
water at the maximum rate. With more or less storage the capacity 
of the source can be more or less reduced. 

29. Monthly Variations .—In nearly all cases the rate of consump¬ 
tion reaches a maximum in the summer owing to the use of water for 
street- and lawn-sprinkling. This high rate usually extends over two 
or three months. A secondary maximum often occurs in the winter, 
due to the waste of water to prevent freezing, but the use of meters 
will largely prevent excessive variations from this cause. In extreme 
cases, however, the winter consumption may be very high. For 
example, during the severe winter of 1898-99 service-pipes quite 
generally froze in many places in the Northwestern States, and in some 
of these towns the waste of water to prevent further freezing raised the 
daily consumption to 300 or 400 gallons per capita for several weeks. 


VARIA 7'10NS IN CONSUMPTION. 


27 


The occurrence of a large fire at such a time would be likely to prove 
disastrous. Such a contingency should, however, be met by using a 
more ample margin of safety in the depth at which the pipes are laid, 
and need only be considered to a slight extent as a possible element 
in causing high consumption. 

The monthly variations in consumption for several places are illus¬ 
trated by the curves of Fig. 4; and further data relating to monthly 
rates are given in Table No. 3. The data are mostly for 1896. 



Fig. 4.—Ratios of Monthly to Average Consumption. 


From the diagrams and table it may be concluded that the maxi¬ 
mum monthly rate will seldom exceed 125 per cent of the average, 
it being in fact much below this figure for most places represented. 
The diagram further shows that excessive consumption is likely to con¬ 
tinue for two or three consecutive months, averaging for this longer 
period a rate of 110 to 11 5 per cent of the yearly average. 

30. Daily Variations .—The maximum daily rate is usually esti¬ 
mated at about 150 per cent of the average. In Table No. 3 very 
considerable differences are to be noted in the ratios for different places, 
these being caused by a variety of conditions, some accidental and 
















































28 


QUANTITY OF WATER REQUIRED. 


TABLE NO. 3 . 


MAXIMUM MONTHLY AND DAILY RATIOS EXPRESSED AS PERCENTAGES OF AVERAGE 


CONSUMPTION. 


City. 



Chicago. 

Philadelphia 

Boston. 

Cincinnati.. , 
Cleveland... 

Buffalo.. 

Detroit. 

Milwaukee.. 


108 
i io 
114 
124 
114 


117 

113 


116 

122 

119 

153 

146 

168 

150 


City. 

Ratio of Maximum 

Monthly to Average 

Consumption. 

Ratio of Maximum 

Daily to Average 

Consumption, 

Louisville. 

127 

135 

Columbus. 

107 

157 

R i v r ... 

11 c 


Dayton. 

Il8 

17S 

Newton. 

125 

143 

Pawtucket... 

111 

153 

Woonsocket, R. I. 

122 

155 

Marquette, Mich. 

139 

194 


some constant. Few of the ratios, however, are much above 150 per 
cent, Which may be taken as a value not likely to be greatly exceeded. 
The maximum daily rate will usually occur in the month of maximum 
consumption, and a rate considerably above the average for the month 
will obtain for several consecutive days. Thus where the maximum 
daily consumption is 150 per cent of the average, the maximum weekly 
consumption is likely to be from 130 per cent to 140 per cent of the 
average, but for longer periods of time the rate will approach the 
monthly maximum. 

31, Ordinary Hourly Variations. —If there were no waste or leak¬ 
age, the consumption during several hours of the night would be almost 
nothing and the relative variations in consumption throughout the 24 
hours would be very great. Whatever leakage exists is nearly constant 
and tends therefore to decrease these variations. During the summer, 
when the monthly rate is high, the hourly rate is also likely to be high, 
as the excessive use of water at that time of the year is largely due to 
lawn- and street-sprinkling, which usually occurs at a time of day when 
the consumption for other purposes is large. This results in a very 
high hourly rate. To prevent this excessive rate many towns have 
regulations requiring the sprinkling of lawns to be done at special hours 
when the demand for other purposes is somewhat lessened. The con¬ 
sumption in the winter, although it may be great, is more uniform 
throughout the 24 hours, as the waste at this time of year will be the 
greatest at night. In small cities the demand is likely to be more 
irregular than in large cities. 






































VARIATIONS IN CONSUMPTION. 


2 9 


Measurements made in 
Mystic works, the following 
of the day: 

1 to 4 A.M. 

Boston in August, 1893, gave, for the 
rates of consumption for different portions 

Rates per Head per Day. 

4 to 7 “ . 


7 to 10 “ . 


IO A.M to I P.M.. 


I tO 4 P.M. 


4 to 7 “ .. 


7 to IO P.M. 

IO P.M. tO I A.M. 


Average. 



The maximum rate for 3 hours was thus 103.8 gallons, or 141 per cent 
of the average; and from 7 A.M. to 7 P.M. the rate was 127 per cent 
of the average for the day. Referring to Table No. 3 and assuming 
the variation on the day of greatest draught to be the same as here 
given, the maximum draught from 7 to 10 A.M. for the year would 
then be 141 per cent of 119 per cent = 168 per cent of the daily 
average for the year. The large consumption from 1 to 4 A.M. must 
have been mostly waste. 

In Detroit the maximum hourly demand in 1894 and in 1895 was 
178 per cent of the average yearly rate. 

Mr. Coffin found for Attleboro, Mass., (population 7577 in 1890,) 
a rate for the maximum month of 122 per cent of the average yearly 
rate, maximum week 134 per cent, maximum day 155 per cent, maxi¬ 
mum hour of maximum day 333 per cent, maximum two continuous 
hours 312 per cent, and minimum hour 45 per cent. The average rate 
from 10 A.M. to 3 P.M. for three days in the month of maximum con¬ 
sumption was 230 per cent of the average A 

In Fig. 5 are plotted, for two days each, the hourly rates of con¬ 
sumption, expressed as percentages of the average hourly rate for the 
entire day, for the cities of New York City,t Rochester ,X N. Y., 
Binghamton,^ N. Y., Des Moines,§ la., Rockford, || Ill., and Rock 
Island, If Ill. For the city of Rockford the high consumption during 
sprinkling hours, 6 to 8 P.M., is notable, and for all places the large 
consumption during the night. The total per-capita consumption of 
these places was for 1895 approximately as follows: New York City, 

* Trans. Am. Soc. C. E., 1897, xxxvm. p. 27. 

f Report of J. R. Freeman on the water-supply of New York City, 1900. 

tOgden. Sewer Design (New York, 1899). 

§ Eng. News , 1896, xxxv. p. 130. 

| Reports of city officers, 1895. 
f Report by D. W. Mead, 1895. 
















30 


QUANTITY OF WATER REQUIRED. 


too gallons; Rochester, 71 gallons; Binghamton, 135 gallons; Des 
Moines, 43 gallons; Rockford, 90 gallons; and Rock Island, 200 
gallons. It will be noted that, in general, those places having the 
largest consumptions show the smallest percentage variation through¬ 
out the day. This is due to the excessive leakage and waste which 
occurs in these places, and which is nearly uniform.* If the maximum 
ratios of the diagrams be multiplied by the maximum daily ratio of, 


A. M. 


P M. 


A. M- 


R M. 



Fig. 5.—Hourly Variations in Consumption. 
say, 150 per cent, there results for the maximum hourly ratios for the 
entire year the values 175, 210, 180, 238, 220, and 183 per cent, 
respectively. Regarding rates for longer periods than one hour it is 
to be noted from the diagram that a rate nearly equal to the maximum 
is likely to continue for 4 or 5 hours. 

32. Consumption for Large Fires. — Large fires occur but seldom, 
and in most of the statistics already given, especially those relating to 
hourly rate, it is safe to say that nothing more than an ordinary fire 
has been involved, such as would require much less than the maximum 


* This point is well brought out by Mr. J. R. Freeman in his report on the water- 
supply of New York City, in which he shows graphically that the hourly rates of 
consumption of New York, Brooklyn, Fall River, and Woonsocket differ by nearly a 
constant quantity, although the average daily consumptions are widely different. 
(See Ettg. Record , 1900, xlii. p. 103.) 



























































































VARIATIONS IN CONSUMPTION. 


51 


rate of supply. The consumption for large fires must then be consid¬ 
ered in addition to the rates given above. 

The maximum rate of fire consumption in gallons per capita per 

day for a town or city of average character may be taken equal to IQQ ° , 

V x 

where at == population in thousands. This is based on Kuichling’s 
estimate of the required number of fire-streams,* and assumes 250- 
gallon streams. 

If the average consumption is 100 gallons per capita, then the fire 
rate in per cent of the average will be as follows for different-sized 
cities: 

Rate of Fire Consumption in Percentage 

Population. of Average, when Average equals ioo 

Gallons per Day. 


1,000 

5,000 

10,000 

50,000 

100,000 

200,000 

300,000 

500,000 


1000 per cent. 


447 

« 

316 

« 

141 

• 

100 

* 

7i 

1 

58 

4 

45 

i 


For other average values of the daily consumption the percentages 
would vary accordingly, being greater for smaller consumptions. In 
the case of small cities the fire rate is evidently the principal factor to 
be considered; in large cities it is of much less relative importance. 
The duration of the above rate of fire consumption may be several 
hours; it has been estimated by Freeman at about six hours as a maxi¬ 
mum for the full number of streams. 

33 . Maximum Hourly. Rate. —The chance of a large fire occurring 
at the same time as the maximum consumption for other purposes is 
exceedingly remote, so that in obtaining the probable hourly maximum 
some reduction may be made in the figure obtained by combining both 

maxima. 

The maximum hourly rate for a city of 50,000 inhabitants, with 
100 gallons per capita as the average consumption, may, for example, 

be estimated about as follows: 

Maximum daily ratio = 150 per cent of average. 

Max. hourly ratio of maximum daily = 150 per cent of 150 per cent 

= 225 per cent of average. 

Fire consumption.= l 4 l 

Total.= 366 “ “ “ “_ 

' Am. Soc. C. E., 1897, xxxvm. p. 16. For further discussion of this 

subject see Chapter XXVIII. 






















QUANTITY OF WATER REQUIRED. 


32 

This total may be reduced to, say, 340 per cent of the average, or 340 
gallons per day, as the maximum rate. It would not, however, be safe 
to assume a much lower rate, as the average daily for an entire month 
is likely to be 125 per cent of the average, which would give for the 
ordinary hourly maximum 125 X 15° — 187 P er cent. Adding the fire 
demand, the maximum becomes 328 per cent, or 328 gallons per day. 

34. Consumption in European Cities.—The consumption of water in 
European cities is much less than in American cities. 1 his is due in 
part to the more general use of meters in Europe, but it is also 
undoubtedly true that water is used less lavishly and wastefully there 
than here. Moreover, in the United States much more water is lost 
by leakage, the pipes usually being much larger and in many cases 
probably not so well laid. It is believed, however, that a considerable 
part of the difference is due to a greater legitimate demand in this 

TABLE NO. 4 . 

CONSUMPTION OF WATER IN EUROPEAN CITIES. 


City. 


England, 1896-97:* 

London. 

Manchester. 

Liverpool. 

Birmingham. 

Bradford. 

Leeds. 

Sheffield. 

Nottingham. 

Brighton. 

Plymouth. 

Germany, 1890 (Lueger): 

Berlin. 

Breslau... 

Cologne. 

Dresden. 

Dtisseldorf... 

Stuttgart. 

Dortmund. 

Wiesbaden. 

France, 1892 (Bechmann): 

Paris. 

Marseilles. 

Lyons.. 


Estimated 

Population. 

Consumption per Capita 
Daily. Gallons. 

City. 

Estimated 

Population. 

, Consumption per Capita 
Daily. Gallons. 



1 

France, 1892 (Bechmann): 



5,700,000 

42 

Bordeaux. 

252,654 

58 

849,093 

40 

Toulouse. 

148,220 

26 

790,000 

34 

Nantes. 

125,000 

13 

680,140 

28 

Rouen. 

107,000 

32 

436,260 

31 

Brest. 

70,778 

3 

420,000 

43 

Grenoble. 

60,855 

264 

415,000 

21 

Other countries, 1892-96 



272,781 

24 

(Bechmann): 



165,000 

43 

Naples. 

481,500 

53 

98,575 

59 

Rome. 

437.419 

264 



P lorence. 

192.OOO 

21 

1,427,200 

18 

Venice . 

130,000 

11 

330,000 

20 

Zurich . 

80,000 

60 

281,700 

34 

Geneva . 

70,000 

61 

276,500 

21 

Amsterdam . 

515,000 

20 

144,600 

25 

Rotterdam. 

240,000 

53 

139,800 

26 

Brussels. 

489.500 

20 

89,700 

78 

Vienna. 

1,365,000 

20 

62,000 

20 

St. Petersburg . 

960,000 

40 



Bombay. 

810,000 

61 

2,500,000 

53 

Sydnev. 

423,600 

38 

406,919 

202 

Buenos Ayres. 

680.000 

34 

401,930 

3 i 

1 





* Compiled, except the figures for London, by Hazen. Eng. News, 1899, xli. p. m. 











































































GROWTH OF CITIES. 


33 


country; a demand caused in some cases by a higher commercial con¬ 
sumption and in general by a larger domestic use due to the less 
economical habits of the people and to the use of a larger number of 
fixtures. In Table No. 4 is given the consumption per capita for 
several cities in various European countries. 

The use of water for public purposes in seven German cities varied 
from 1 to 12 gallons per capita in 1888—1890, this being from 2 per 
cent to 33 per cent of the total consumption. In Berlin 2.5 per cent 
is used for street-sprinkling, 3 per cent for sewer-flushing, and 7 per 
cent for fountains. In Dresden 3.7 per cent of the entire consumption 
is used for public fountains.* In Paris 35 per cent, or 20 gallons per 
capita, is used for street-washing. 



35. Growth of Cities.—A necessary factor in any estimate of future 
consumption is that of future population. The rate of growth of differ¬ 
ent cities is exceedingly various, but of any one city it is likely to be 


* Handbuch der Ingenieurvvissenschaften, p. bg. 































34 


QUANTITY OF WATER REQUIRED. 


fairly constant for several years, or at least will vary but slowly. The 
older and the larger the city the more uniform the rate of growth, and, 
barring national disasters, a fairly close estimate can be made for two 
or three decades in the future. In the case of many American cities 
the rate is still undergoing large variations, and predictions are very 
uncertain. 

For a city with a steady rate of growth the percentage added each 
decade or shorter period is very nearly constant; and to estimate the 
future population it is only necessary to apply this constant percentage 
successively for as many periods as desired. If the percentage is 
changing, then a varying rate must be used, which can only be pre¬ 
dicted by a study of the changes in the rates in past years and a 
knowledge of such local conditions as are likely to affect the city’s 
growth. To facilitate such estimates the percentage increase for each 
decade should be plotted, and any marked tendency to change can then 
be allowed for in extending the curve forward. 

In Fig. 6 are plotted such percentages for several cities of differing 
characteristics. The percentages for London are remarkably constant, 


o 


2100000 


2P00P00 


1300000 


I 

& 


1 , 000,000 


500,000 











A * 

7 ? 

* 

/ 

/ 











(5 

0 

07 

/ 

/ 



* 

* 

* 









0 

vw 

rne 











v\C 

m? 

€■ 

/ / 
%* 

W 

fp'’ 

* 









# 


* 











. e, 

ErN 











F 

pilSi 

W 

'// 














f 

Bosior, 

Londa 

fTen- 
7 (/one 

7h/e C/f 
rC/rc/t 

z/ej 

’) 

Pop. 

%70c 

V m 

/60A 

/602 


J 

0?' 




Ber//r, 

Pb/Iao 

'Tr/rff? 

(/nc/ut 

Oof/af 

7-rm/eL 

bng<St 

Ten-m/f 

frc/e) 

tburbs 
’ C/rcA 

1 ' 

’/ . 

• 

- 

7835 

1672 

/662 







Ch/cat. 

io 

• 

- 


- 

* 

1686 



£5 20 /5 /0 5 0 5 /0 /5 20 25 30 35 

Years Before and Affer Peocb/ng a Popufaf/on of 36 7,000 


Fig. 7.—Population Curves Plotted with Reference to Boston, Mass. 
and in estimates for the future a rate of 20 might reasonably be 
assumed. Several of the other cities have reached a nearly uniform 
rate, while in some the rate is still likely to undergo great changes. 
In estimating the population of London for forty years in the future the 
Royal Commission in 1893 used the percentage for the decade 1881 to 
1891, a value of 18.2. The data for Boston, New York, Philadelphia, 



























GROWTH OF CITIES. 


35 


and Chicago are as compiled by Brackett in Appendix No. I of the 
Report of the State Board of Health of Massachusetts upon a Metro¬ 
politan Water-supply. They represent in each case the population 
within a i 5 mile radius. 

36. Another method of estimating future population is to study the 
growth of various larger cities from the period at which their population 
equaled the present population of the city in question; and, taking 
account of differing characteristics, to deduce therefrom the probable 
future population required. This method was used as an aid in predict¬ 
ing the future population of Boston in the report above referred to, and 
the diagram employed is reproduced in Tig. 7. It exhibits the curves 
for several cities, so plotted as to intersect at the point corresponding 
to a population of 967,000, the population of Boston in 1894. 

An objection to this method of estimation is that it is based upon a 
comparison of rates of growth of cities of widely varying characteristics, 
and of rates relating to very different periods of time. Thus the growth 
of Boston in 1900 is compared with that of New York in i860, when 
industrial conditions were materially different from those at the present 
time. 

LITERATURE. 

1. Harlow. The Consumption and Waste of Water delivered by Public 

Works. Trans. Am. Soc. C. E., 1877, vi. p. 107. 

2. Brush. Some Facts in Relation to Friction, Waste, and Loss of Water 

in Mains. Trans. Am. Soc. C. E., 1888, xix. p. 89. 

3. Manual of American Water-works. 1890-1 and 1897. 

4. Freeman. The Arrangement of Hydrants and Water-pipes for the Pro¬ 

tection of a City against Fire. Jour. New Eng. W. W. Assn., 1892, 
vii. p. 49 

5. Report of the Royal Commission on the Water-supply of the Metropolis. 

London, 1893. 

6. Halbertsma. Dichtigkeitsproben an Rohrnetzen. Jour. f. Gasbel. u. 

Wasservers., 1894, xxxvn. p. 722. 

7. Brackett. Consumption and Waste of Water. Trans. Am. Soc. C. E., 

1895, xxxiv. p. 185. 

8. Kuichling. The Financial Management of Water-works. Trans. Am. 

Soc. C. E., 1897, xxxviii. p. 1. 

9. Crandall. Loss of Water from Pipes. Jour. New Eng. W. W. Assn., 

1898, xii. p. 245. 

10. Report on the Extension and Improvement of the Water-supply of Phila¬ 
delphia, 1899. Abstract, Eng, News , 1899, xlii. p. 230; Eng. 

Record , 1899, xl. p. 404. 

n Freeman. The Water-waste and Water supply of New York City. 

Report to the Comptroller. 1900. 

12. The Water-supply of the City of New York. 1900. Issued by the 

Merchants’ Association. Contains reports by J. J. R. Croes and 

Foster Crowell on the use and waste of water. 


CHAPTER III. 


SOURCES OF SUPPLY. 


37. Classification.—The sources of water-supply may be divided 
into the following classes according to the general source and the 
method of collection: 

A. Surface-waters: 

1. Rain-water collected from roofs, etc. 

2. Water from rivers. 

3. Water from natural lakes. 

4. Water collected in impounding reservoirs. 

B. Ground-waters: 

5. Water from springs. 

6. Water from shallow wells. 

7. Water from deep and artesian wells. 

8. Water from horizontal galleries. 

Each of the above sources except the first and last are at present fur¬ 
nishing many cities in the United States with a more or less satisfactory 
water. 

38. Quality of Water from Various Sources.—The kind of water 
which a region can furnish depends on its climatic, geologic, and topo¬ 
graphic features. Much good water has been obtained from small 
streams in the rougher portions of the United States where sites for 
reservoirs can readily be found and where collecting areas are sparsely 
populated; but in a large portion of the country such a source of supply 
is impracticable or undesirable, and in these localities we find that the 
ground-water supplies have been more largely developed. Many 
supplies drawn from lakes and rivers are also in use in all parts of the 
country, but until some method of purification is generally adopted they 
will not be as a rule very satisfactory. These sources must, however, 
continue to furnish a large and increasing number of cities with water 
as the supplies from the first-mentioned source become more and more 
fully utilized. 

Ground-waters are as a rule of better quality from a sanitary point 

36 




UTILIZATION OF THE VARIOUS SOURCES. 


37 


of view than surface-waters, but in many cases they will not be 
altogether satisfactory until processes for the removal of iron and of 
hardening impurities are adopted. 

39. Utilization of the Various Sources.—The following table gives 
the number of water-works obtaining their supply from the various 
sources indicated, and the percentage of the total number supplied from 
each source. Under Northeastern States are included Pennsylvania, 
New Jersey, and all to the north and east; North Central includes all 
others to the north of the Ohio River and east of the Mississippi River; 
Southeastern, all remaining States east of the Mississippi; and Western, 
all west of it.* 


TABLE NO. 5 . 

SOURCES OF WATER-SUPPLIES IN THE UNITED STATES. 


Source. 


Surface-waters: 

Rivers.. 

Lakes. 

Impounding reservoirs. 

Combinations. 

Total. 

Ground-waters. 

Shallow wells. 

Artesian wells. 

Springs. 

Galleries and tunnels. 

Combinations. 

Total. 

Surface- and ground-waters. 

Rivers and ground-waters. 

Lakes and ground-waters. 

Imp. reservoirs and ground-waters 

Total. 


No. of Works. 


Northeastern 

States. 

Southeastern 

States. 

North Central 
States. 

Western 

States. 

Total 

Number. 

Per cent of 

Grand Total. 

336 

Il6 

117 

256 

825 

24.6 

129 

6 

62 

24 

221 

6.6 

135 

20 

12 

46 

213 

6-3 

J 5 

I 

2 

3 

21 

0.6 

615 

143 

193 

329 

1280 

38.2 

130 

41 

310 

380 

86l 

25-7 

39 

59 

98 

145 

341 

10.1 

300 

72 

27 

103 

502 

14.9 

9 

0 

12 

13 

34 

1.0 

33 

8 

22 

21 

84 

2-5 

5ii 

180 

469 

662 

1822 

54-2 

92 

16 

37 

6l 

206 

6.1 

11 

0 

l6 

4 

3i 

0.9 

9 

1 

O 

7 

17 

c -5 

112 

17 

53 

72 

254 

7.6 

1238 

340 

715 

1063 

3356 

100.0 


Grand total 


The number of filtered supplies in 1896 was as follows: 


Surface-waters. 179 

Ground-waters. 23 

Surface- and ground-waters. 29 


Total. 231 


* From Eng. News , 1898, XL. p. 9, and Manual Am. W. W., 1897. 

























































































33 


SOURCES OF SUPPLY. 


In Europe a much larger proportion of the public supplies is derived 
from ground-water sources than is the case in this country. In 
Germany, for example, in 1884, of the total population having a public 
water-works the following percentages drew their supply from the 
various sources indicated: * 


River- and other surface-water. 27.9 per cent. 

Spring-water. 13-8 “ 

Other ground-water. 58-3 


In France, out of a total population of about 12 millions living in 

cities of over 5000 inhabitants, the following percentages were, in 

1892, supplied with water from the sources indicated: + 

Rivers. 14 per cent. 

Springs. 23 “ “ 

Other ground-water. 14 “ “ 

Combinations. 49 “ 41 


* Jour. f. Gasbil. u. Wasservers., 1884, p. 411. 
f Bechmann. Distribution d’eau (Paris, 1899), 11. p. 330. 










CHAPTER IV. 


THE RAINFALL. . 


40. The rainfall being manifestly the source of all water-supply, 
whether caught as it flows over the surface or first allowed to percolate 
into the ground to furnish water for wells and springs, it is desirable 
to commence the discussion of the quantity available from the different 
sources with a study of the rainfall. The yield of a given source is the 
product of several factors, of which the rainfall is but one; and in many 
cases it is quite as easy or even easier to estimate the value of this 
product directly as to determine it from a consideration of the several 
factors. In other cases, however, this cannot be done, and to enable 
the data already collected regarding the various elements to be intelli¬ 
gently used in the solution of new problems, a careful study of each of 
these elements is necessary. 

41. Measurement of Rainfall. —The amount of rainfall is expressed 
in inches of depth upon a horizontal surface, snowfall being reduced to 




Fig. 8.—Ordinary Rain-gauge. 


its equivalent amount of rainfall. The ordinary rain-gauge used by 
the Weather Bureau is illustrated in Fig. 8. The diameter of the 

39 







































































40 


THE RAINFALL. 


receiver A is 8 inches, and the entire height of the instrument is 
2 feet. The rim is beveled to a sharp edge and is accurately circular. 
The water which falls into the receiver is conveyed into the collecting- 
tube C y of one-tenth the cross-section of the receiver, and the amount 
of water so collected is determined by a measuring-stick of cedar. In 
this way small rainfalls can be readily measured. Large rainfalls 
overflow into the outer cylinder, which is also used as a collector for 
snow. 

While the actual measurement is thus simple, the collection of the 
correct amount of water is not easy. It is found that the amount of 
water collected depends largely upon the location of the gauge. 
Variations as great as 50 per cent have been observed, due to differ¬ 
ences in location in regard to buildings and other objects, and to the 
elevation of the gauge above the ground. In general the greater the 
elevation of the gauge the less the amount of water collected. The 
reason for this has been quite conclusively shown to be due to the 
greater velocity of the wind at the greater elevation, less water being 
collected the stronger the wind.* 

The errors of collection due to wind eddies caused by buildings, 
trees, etc., are of much greater importance than those due to elevation, 
and to avoid these the gauge should be located some distance from all 
disturbing objects and not much above the ground. In cities, the best 
place is on the roofs of flat buildings, and this is the location usually 
selected by the Weather Bureau. Such locations, though free from 
disturbances caused by other buildings, are not as trustworthy as Is 
desirable, and it is estimated by the Bureau that the amounts regis¬ 
tered by its gauges are from 5 to 10 per cent too small. + 

Besides inaccuracies due to exposure, there are slight inaccuracies 
in the measurement of small rainfalls in dry weather due to evaporation 
Irom the gauge, and very considerable errors in the measurement of 
snowfalls. 

With the ordinary rain-gauge it is impracticable to determine rates 
of rainfall for short periods of time, the records usually obtained from 
these gauges being merely the total amounts of rainfall for each 
twenty-four hours. For estimating flood-volumes from small areas, 
however, it is important to know the rate of rainfall for much shorter 
periods than one day. For this purpose self-recording gauges are 
essential, that is, gauges which give a continuous record of the rainfall 
or a record taken at such short intervals as to be for all practical pur- 


* See reference (2), p. 50. 
f Bulletin D, Weather Bureau, 1897, p. 9. 



RA IN FA LL S TA T IS TICS . 


41 


poses continuous. Various forms have been devised, some weighing 
the water, others recording by volume.* 

42. Rainfall Statistics for a large number of stations can now be 
readily obtained from the monthly reports of the Weather Bureau. 
Since 1888 observations relating to excessive rainfalls have been made 
with self-recording rain-gauges, the number of stations provided with 
such gauges in 1900 being about seventy. The data of importance in 
connection with water-supply questions are the mean yearly rainfall, 
the deviation from this in dry years, the monthly rainfall, and finally 
the maximum depth of rain falling in a single day or less. 

43. Mean Annual Rainfall. —The mean annual rainfall of the United 
States is graphically shown in the map of Fig. g.f This map is based 
upon the records of all Weather Bureau stations from 1870 to 1896, 
supplemented by records of voluntary observers. The maximum rain¬ 
fall is seen to be along a narrow belt of the North Pacific coast, where 
it considerably exceeds 60 inches. Towards the interior the amount 
rapidly falls off, and between the Sierras and the Rocky Mountains it 
ranges from 5 to 1 5 inches. East of the Rockies there is a gradual 
increase eastward and southward to a maximum along the Gulf of 60 
inches, and from 40 to 50 inches on the Atlantic coast. 

44. Secular Variations in the Rainfall.— The question of a gradual 
change in the yearly rainfall is one the solution of which would doubt¬ 
less require data covering several centuries. The rainfall for a partic¬ 
ular locality may average considerably below the mean for many years,, 
after which may follow, perhaps, an equally long period of surplus. 
In an analysis of several records extending over many years it was; 
found that during an 83-year period at New Bedford, Massachusetts, 
the averages for 10-year periods were as high as 16 per cent above the 
mean and 11 per cent below; for 60-year periods the extremes were, at 
St. Louis, 17 per cent and 13 per cent, and at Cincinnati, 20 per cent 
and 17 per cent. For a 2 5-year period the extreme variations were 
10 per cent for both New Bedford and St. Louis.:); From this it is seen 
that to establish a reliable mean it requires a record extending over a 
long period of time. 

The variations or cycles above referred to, that extend over several 
years, are in some cases very marked, but they are very erratic and as 
yet quite incapable of being predicted. In Fig. 10 are plotted what 

* For a description of various forms of self-recording gauges see references (7) 
and (9), p. 51. 

f From Bulletin D, Weather Bureau, 1897. 

\ Bulletin D. 







42 


THE RAINFALL . 


are called progressive averages of precipitation for three sections of the 
country, and the actual precipitation for Madison, Wisconsin, for a 



'number of years. The progressive averages for each section are found 
by first averaging the yearly rainfalls for three or four stations; then 


Fiu q.—Mean Annual Rainfall of the United Staies. 




































SECULAR VARIATIONS IN THE RAINFALL. 


43 


these averages are further modified to give a smoother curve by the 
formula 

t ci —J— /\.b 6 c -]— /\.d —j— e 
C = 16 ’ 



where a, c, d, and e are the rainfalls for successive years, and c' is 
the progressive average for the middle year. In this way any gradual 
change in the rainfall can be more clearly brought out. In the 
diagram the ordinates represent inches above or below the mean. The 
gradual increase for a long period of time in the rainfall at the stations 
representing New England is very striking, although this is shown by 
other records to be quite local in extent. Other changes for consider¬ 
able lengths of time are to be noted in the diagram, and it is clearly 
to be seen that a record covering twenty or thirty years is of no value 
in studying the question of secular variation. The diagram for 








































































































44 


THE RAINFALL. 



Madison, Wisconsin, is of course very rough, but shows the same 
general variation as that just above it. If the portion of the curve for 
the years 1880 to 1895 alone be considered, a very rapid and persistent 

decrease in the rainfall would be noted. 

45. Mean Monthly Rainfall. —The monthly distribution of the rain¬ 
fall is of great importance in all questions relating to the utilization of 
water for power purposes or for the supply of cities. I he rain falling 
in the summer months, when vegetation is using a maximum of water 
and evaporation is rapid, is of but little value for supplying water to the 
streams. It is the winter and spring rains which must largely be relied 
upon to fill reservoirs and to raise the low ground-water to its normal 

level. 

Fig. 11 * shows graphically the mean monthly distribution of the 
rainfall for several stations representative of the different sections of the 




■1 



Fig. 11.—Monthly Variations in Rainfall. 
country. The ordinates represent the percentage of the total yearly 
rain falling in the month. 

In the eastern and southern parts of the country the distribution is 
quite uniform, the variation here being greatest along the south Atlantic 
coast, as shown in the diagram for Charleston. As we go farther 
north and west to Detroit, Madison, and North Platte, a great change 


* B u 11 e t ■ n D. 

























































































































































































MINIMUM YEARLY RAINFALL. 


45 


takes place, a larger and larger percentage of the rain falling in the 
summer months. This is a very advantageous distribution for vegeta¬ 
tion, but a very poor one for furnishing surplus water. The diagram 
for Santa Fe is typical of New Mexico and Arizona, and that for 
Spokane of the northern plateau. The distribution along the entire 
Pacific coast is very similar to that at San PTancisco. 

Numerical data relating to the distribution of the yearly rain are 
given in Table No. 6. 

46. Minimum Yearly Rainfall. —In Table No. 6 are given, for 
several representative stations, the mean yearly rainfall; the propor¬ 
tion of the yearly rain falling during the six months from June to 
November, inclusive; the percentage of the mean yearly rain which 
fell in the driest year covered by the records; the percentages for the 
two driest consecutive years, and likewise for the three driest consecu¬ 
tive years; and the number of years of records from which the data 
have been collected. The records close with 1896. 

TABLE NO. 6. 


GENERAL RAINFALL STATISTICS FOR THE UNITED STATES. 


Station. 

Mean Yearly Rain¬ 
fall. 

Per cent of Summer 
and Autumn Rain 
to Mean Yearly. 

Per cent Driest Year 
to Mean Year. 

Per cent Two Dri¬ 
est Years. 

Per cent Three Dri¬ 
est Years. 

Number of Years’ 
Record. 

North Atlantic : 





80 



45-4 

50 

60 

70 

79 


45-8 

52 

74 

78 

82 

45 


44.7 

52 

62 

77 

80 

61 


42-3 

52 

70 

75 

80 

72 


42.9 

51 

69 

7 i 

74 

45 

South Atlantic: 





81 

26 


53-7 

6l 

75 

80 


49.1 

6l 

48 

55 

62 

89 


48.0 

50 

81 

88 

87 

27 


54-1 

&5 

74 

77 

83 

27 


38.2 

70 

54 

61 

73 

49 

Gulf and Lower Mississippi: 



67 





48.2 

43 

75 

75 

25 


52.5 

42 

76 

80 

83 

24 


62.6 

5 i 

68 

75 

78 

26 


60.3 

52 

64 

75 

77 

26 


47-7 

58 

50 

65 

72 

26 


50.2 

46 

67 

73 

83 

32 


52.7 

43 

70 

74 

83 

42 

Ohio Valley: 

36.6 



78 

85 



53 

70 

54 


42.1 

50 

60 

72 

7 i 

62 


42.2 

5 i 

59 

76 

82 

27 


47.2 

48 

74 

81 

85 

25 


12.6 

47 

62 

75 

81 

25 

















































46 


THE RAINFALL. 


TABLE NO. 6.— Continued. 


GENERAL RAINFALL STATISTICS FOR THE UNITED STATES. 


Station. 

Mean Yearly Rain¬ 

fall. 

Per cent of Summer 

and Autumn Rain 

to Mean Yearly. 

Per cent Driest Year 

to Mean Year. 

Per cent Two Dri¬ 

est Years. 

Per cent Three Dri¬ 

est Years. 

Number of Years' 

Record. 

Lake Region: 







Marquette. 

32.3 

58 

69 

75 

8 l 

33 

Detroit. 

32-5 

56 

65 

72 

79 

46 

Cleveland. 

36.6 

54 

71 

74 

81 

41 

Duluth. 

30-7 

63 

65 

81 

88 

26 

Upper Mississippi Valley: 




t 


St. Louis. 

40.8 

52 

55 

65 

75 

60 

Davenport. 

33-3 

58 

56 

68 

73 

26 

Chicago... 

34-0 

54 

66 

80 

86 

30 

Milwaukee. 

31.0 

55 

66 

74 

73 

53 

Madison. 

33-2 

58 

39 

58 

68 

28 

La Crosse. 

30.7 

65 

57 

78 

79 

24 

St. Paul. 

28.2 

63 

53 

54 

75 

39 

The Plains: 






Omaha. 

3i-4 

63 

57 

63 

70 

27 

Dodge City. 

19.8 

62 

5i 

58 

73 

22 

North Platte. 

18 . 1 

61 

56 

67 

72 

22 

Denver. 

T 4-3 

48 

59 

7i 

77 

27 

Cheyenne... 

12.7 

55 

39 

62 

75 

27 

The Plateau: 





Y uma. 

2.8 

39 

25 

50 

46 

21 

Phoenix. 

7-i 

49 

52 

88 

90 

13 

Tucson... 

11.7 

65 

44 

79 

80 

19 

Santa F 6 . 

14.6 

69 

53 

63 

66 

37 

Carson City. 

12.1 

25 

57 

63 

72 

19 

Salt Lake City. 

18.8 

39 

55 

64 

74 

29 

Spokane.. 

18.6 

38 

73 

84 

84 

15 

Walla Walla. 

15-4 

38 

46 

81 

86 

27 

Pacific Coast: 





Astoria. 

77.0 

33 

64 

68 

77 

34 

Portland... 

46.2 

3 i 

67 

76 

79 

27 

Red Bluff. 

24.4 

23 

52 

64 

58 

25 

Sacramento. 

19.9 

16 

42 

67 

84 

47 

San Francisco. 

23-4 

17 

5 i 

73 

78 

47 

Los Angeles... 

17.2 

15 

33 

48 

59 

24 

Fresno... 

9-3 

18 

61 

65 

74 

19 

San Diego. 

9-7 

18 

30 

54 

1 61 

47 


By an examination of data relating to stream-flow it is found that 


the months from June to November are the six months in which the 
rainfall has in general the least direct effect upon stream-flow. The 
percentages of the yearly rain falling in these months have therefore 
been given in the table. 

In England it was formerly the practice in designing water-works 
to assume as the mean rainfall for the three driest years 83^ per cent 
of the mean, but further investigation led to the adoption of 80 per cent 
as a more reliable figure. Similar ratios have also been made use of 

























































MAXIMUM RATES OF RAINFALL,, 


47 


to a considerable extent in this country, but from the above table it is 
evident that in many localities it would not be safe to use over 75 per 
cent, or even less. The very low percentages for some of the stations 
must be taken as an indication of what may occur at any point in a 
comparatively wide territory in each case. For example, at Madison, 
Wisconsin, the rainfall in 1895 was but 39 per cent of an average, and 
this was both preceded and followed by years of low rainfall, thus 
giving the very low percentages of 58 and 68 for the two and three 
driest years. This extreme drought was very local, but it shows what 
may happen at rare intervals in that part of the country. 

The lowest percentages for the one, two, and three driest years, 
with the exception of a few extreme cases, are about the same over a 
large portion of the United States and may reasonably be placed at 
about 60, 70, and 75 per cent for the East and South, with a reduction 
to 50, 60, and 70 per cent respectively for the Northwest and plains 
region. For the Rocky Mountain region and the Pacific coast the 
figures would in many places be much lower, but the conditions are 
here so varied that a general statement would be of no value. 

47. Maximum Rates of Rainfall. —In estimating the maximum flood- 
volumes of small streams—a matter of very great importance in the 
design of dams and reservoir embankments—it is desirable to know 
the maximum rates of rainfall for periods of a few hours or a single 
day. 

In Table No. 7 are presented data compiled from the Monthly 
Weather Review relating to excessive rainfalls. The records cover 
the period from 1871 to 1898, and all rainfalls are represented which 
exceeded in amount 5 inches in twenty-four hours, and, from 1894 to 
1898, all those which equaled or exceeded 2 inches in one hour. As 
far as possible, the same storm is represented but once for any one 
State, although records may have been received from several stations; 
and furthermore each storm is counted as a one-day storm or a two-day 
storm, but not both. A one-day storm is one in which all the rain falls 
in a meteorological day, that is, from 8 P.M. to 8 p.m., and in a two-day 
storm all the rain falls within two such days. A one-day storm may 
therefore have fallen in a few hours, and likewise a two-day storm, so 
that the figures given do not necessarily represent the maximum rates. 
However, by taking the maximum from among a great many records 
the figures thus found for the one- and two-day storms will approxi¬ 
mate the maximum for 24 and 48 hours. The one-hour rates are well 
determined. The number of times a rainfall has exceeded the given 
amounts is an indication of the frequency of heavy storms and also 


48 


THE RAINFALL. 


to some extent, of the reasonableness and reliability of the maximum 
figure. Those States having the highest maximum rates are those 
where heavy rainfalls are the most frequent. 

TABLE NO. 7. 

MAXIMUM RAINFALLS. 


State. 

Number of Stations, 
1894. 

Hourly Rate. 

One-day Storms. 

Two-day 

Storms. 

Maximum. 

- J 

No. of Storms 

= or > 2 in.; 

1894-8. 

Maximum. 

No. of Storms 

= or > 5 in. 

Maximum. 

! 

No. of Storms 

= or > 5 in. 

Northern and Central States: 








M nine.. 

18 



e 6 t 

I 

c or 


New Hampshire and Vermont. ... 

41 

3-00 

I 

7.41 

I 

0 • * 1 
6.79 

5 

Massachusetts . 

73 

2.29 

2 

6.60 

2 

8.22 

8 

Connecticut and Rhode Island .. 

29 

4.49 

2 

7.40 

2 

10.30 

9 

New York . 

76 

3-35 

6 

IO. IO 

7 

8.60 

9 

New Jersey . 

59 

2.58 

4 

8-73 

7 

10.40 

12 

Pennsylvania .> 

84 

3-20 

8 

8.37 

10 

9-°3 

4 

Flrlaware. 

7 







Maryland . 

25 

4.64 

1 

7.OO 

5 

u. / <9 

14-75 

1 

3 

Virginia . 

37 

3.00 

7 

7.70 

6 

6.85 

8 

West Virginia . 

39 

2.20 

1 

5-49 

2 

7.00 

1 

Tennessee. 

41 

4.00 

4 

6-57 

14 

9.67 

13 

Kentucky . 

43 

2.9O 

4 

7.02 

5 

8 62 

3 

Missouri. 

96 

4-00 

19 

8.00 

12 

9.60 

17 

Ohio . 

142 

3-32 

10 

5-55 

2 

8.06 

7 

Indiana . 

45 

2.7I 

11 

7.00 

8 

10. CO 

6 

Illinois . 

63 

4-36 

8 

9.08 

17 

9-35 

14 

Michigan . 

86 

3-40 

3 

5 • 5 ° 

1 

6 • 34 

4 

Wisconsin . 

64 

300 

3 

6.94 

5 

10.15 

3 

Minnesota . 

7 i 

3.30 

5 

7.20 

4 

7.80 

6 

Iowa . 

78 

3-90 

10 

8.22 

12 

9.70 

6 

Kansas . 

82 

3-24 

11 

8.23 

14 

8.40 

16 

Nebraska . 

69 

3-10 

10 

12.00 

13 

10.69 

8 

North and South Dakota. 

87 

3- 6 5 

7 

7.70 

5 

6.55 

4 

Colorado. 

79 

3 -o8 

6 

6. 20 

1 

7 • 39 

4 

South Atlantic and Gulf States: 








North Carolina. 

56 

3-43 

14 

9.14 

33 

>-* 

j] 

0 

0 

25 

South Carolina. 

48 

3.00 

7 

10.82 

11 

13.22 

22 

Georgia. 

62 

3-45 

21 

10.38 

25 

11.52 

30 

Florida.. 

34 

4.10 

27 

10. 70 

32 

13-14 

34 

Alabama. 

52 

3-io 

9 

9.00 

28 

10.00 

21 

Mississippi. 

5 i 

2.66 

8 

9.60 

21 

10.60 

21 

Louisiana. 

54 

4.12 

23 

22.27 

61 

16.55 

32 

Texas. 

81 

4.00 

24 

10.15 

36 

13.08 

3 i 

Arkansas. 

48 

3-45 

6 

11.00 

17 

9.10 

20 

Pacific Coast: 








California. 

279 

8.67 

1 

11.50 

16 

22.40 

33 

Oregon and Washington . 

94 



7.12 

8 

10.40 

24 


The curves of Fig. 12 based on the data of Table No. 7 show 
approximately the maximum rainfalls which may be expected for 
















































































EXTENT OF GREAT RAIN-STORMS . 


4 ) 


different lengths of time. The curve for the Northern and Central 
States is somewhat exceeded in a few States, but for most of them it 
represents rainfalls but little greater than those which have already been 
observed, and which may occur again at any time. This curve gives 
a rate of 4 inches for one hour, 8 inches for 24 hours, and 10 inches 
for 48 hours. The curve for the South Atlantic and Gulf States repre¬ 
sents the maximum recorded rainfalls for all the States of this group 
except Louisiana, for which the records far exceed those of any other 



State. For the Pacific coast very high records are also noted at some 
stations.* 

Of especial interest to the hydraulic engineer are the rains which 
occur while the ground is frozen and covered with snow. A study of 
the data shows that in all those States where such conditions could 
obtain, the maximum rates of rainfall for the winter months are con¬ 
siderably below those for the summer months. They are approxi¬ 
mately given by the lower curve of the diagram. The melting of snow 
during an extensive rain may increase the total equivalent by one or 
two inches, thus giving about the same total as the summer curve. 

48. Extent of Great Rain-storms.— That excessive rainfalls are of 
sufficient extent to cover areas of such size as are ordinarily considered 
in water-supply problems is made evident by the statistics of a few 

* For rates for shorter intervals of time than one hour reference should be made 
to various works on sewer design and to papers relating thereto. Among these see 
references (6) to (ro), p. 51 












































50 


THE RAINFALL. 


great storms. In October, 1869, a great storm occurred in the eastern 
part of the United States, with its maximum intensity in Connecticut. 
A careful analysis of the records made by Mr. James B. Francis* 
shows the areas covered by different depths of rain to have been as 
follows: 


Depth of Rain. 

6 inches or more 

y 4 C <4 4 C 

g 44 44 44 

g 44 44 44 

IO 44 44 44 


Area Covered. 


24.431 square miles. 
9,602 
1,824 “ 

1,046 “ 


519 

179 


44 
4 4 


The following are some of the maximum rates observed in this storm: 


4.00 

inches 

in 

2 

hours. 

4.27 

4 4 

< 4 

3 

4 4 

5.86 

4 4 

4 4 

18.5 

4 4 

7 -i 5 

4 4 

4 4 

24 

44 

8.90 

• < 

4 4 

30 

44 

8.44 

4 4 

4 4 

42 

4 4 


The maximum recorded rainfall was 12.35 inches, at Canton, Conn., 
all of which probably fell in about 48 hours. 

The winter storm in New England of February, 1886, was also 
very extensive, it being estimated that 4 inches or more fell over an 
area of 7600 square miles, 6 inches or more over an area of 3000 square 
miles, and 8 inches or more over an area of 750 square miles. + It is 
probably true that some of the most violent storms of the Western 
mountain region, the so-called “cloud-bursts,” are of much greater 
intensity than any represented in the table, but they are very local in 
extent. 


LITERATURE. 

1. Monthly Weather Review , and other publications of the Weather Bureau, 

especially Bulletin C, 1894, and Bulletin D, 1897. 

2. Curtis. The Effect of Wind Currents on the Rainfall. Signal-Service 

Notes No. 16. Contains bibliography. 

3. Francis. Distribution of Rainfall during the Great Storm of October 3 

and 4, 1896. Trans. Am. Soc. C. E., 1878, vii. p. 224. 

4. FitzGerald. Rainfall: Does the Wind cause the Diminished Amount of 

Rain Collected in Elevated Rain-gauges ? Jour. Assn. Eng. Soc., 
1884, hi. p. 233, 

5. The New England Rain-storm of February 10-14, 1886. Eng. News y 

1886, xv. p. 216. 


* Trans. Am. Soc. C. E., 1878, vii. p. 224. 
+ Eng. News, 1886, xv. p. 216. 

























LI TER A TURE. 


5 *■ 


\ 


* 


6. Weston. The Practical Value of Self-recording Rain-gauges. Eng. 

News , 1889, xxi. p. 399. 

7. Rainfall Observations at Philadelphia. Reports Phila. Water Bureau, 

1890-92. Eng. Record , 1891, xxm. p. 246; 1892, xxvi. p. 360. 

8. Talbot. Rates of Maximum Rainfall. The Technograph , 1891-92, 

p. 103. 

9. Self-registering Rain-gauges and their Use for Recording Excessive Rain¬ 

falls. Eng. Record , 1891, xxm. p. 74. 

10. Hoxie. Excessive Rainfalls considered with Especial Reference to their 

Occurrence in Populous Districts. Trans. Am. Soc. C. E., 1891, 
xxv. p. 70. 

11. FitzGerald. Yield of the Sudbury River Watershed in the Freshet of 

February 10-13, 1886. Trans. Am. Soc. C. E., 1891, xxv. p. 253. 


\V * 


CHAPTER V. 

EVAPORATION AND PERCOLATION. 

> 

I 

49. Relation of Evaporation and Percolation to Stream-flow and to 
Ground-water. —Of the rain which falls, a part passes off immediately 
into the streams and forms what may be called the flood-flow; a part 
is evaporated directly from the surface of the ground, from water- 
surfaces, and from the leaves of vegetation; and a portion percolates 
into the ground. Of the last portion a part is caught by vegetation,, 
passed upwards and evaporated or transpired from the leaves (an insig¬ 
nificant portion being retained by the plant), and a part passes on 
downwards and laterally, sooner or later finding its way to the surface 
again in the form of springs, which constitute the source of the dry- 
weather flow of streams. 

The total flow of a stream is then, in general, equal to the rainfall 
less the evaporation; the flood-flow is equal to the rainfall less the 
percolation and evaporation; and finally the dry-weather flow may be 
considered as equal to the deep or more permanent percolation. To 
enable stream-flow data to be used in the most intelligent way in mak¬ 
ing estimates, it is therefore desirable to have a knowledge of the laws 
of evaporation and percolation and of the relative amounts which take 
place under different conditions. Furthermore, as the percolating 
water constitutes the ground-water from which many supplies are 
drawn, this knowledge is of first importance in a study of ground-water 
sources. 

The subject of evaporation naturally divides itself into two parts: 
evaporation from water-surfaces and evaporation from land-surfaces. 
The former is of importance in studying the run-off from watersheds 
having considerable areas of lakes and ponds, and in taking account of 
the evaporation from reservoirs. Considerable reliable information 
exists relating to this part, and the application thereof is easy and direct. 
Evaporation from land-surfaces is, however, much more difficult to 
determine, since the conditions affecting it are so varied and indetermi- 


-2 



EXPERIMENTS ON EVAPORATION FROM WATER-SURFACES . 53 , 

nate; it is therefore only possible to give figures which indicate in a, 

general way the effects of some of the conditions. 

# 

EVAPORATION FROM WATER-SURFACES. 

50. Influences Affecting Evaporation. —The evaporation from the 
free surface of water takes place at a rate depending upon the tempera¬ 
ture of the water at the surface, and upon the quantity of vapor already 
in the air immediately adjacent to it. The former varies not only with, 
the air temperature, but with the depth, nature, and extent of the body 
of water, and with the extent to which it is exposed to wind and sun., 
Fhe latter depends upon the amount of moisture in the air generally, 
and also to a large extent upon the action of wind in removing the 
accumulated vapor from above the water. For any given locality the 
evaporation will vary closely with the variations in mean air tempera¬ 
ture, but for different localities variations in humidity will cause it to 
be very different even though the temperatures are the same. 

51. Experiments on Evaporation from Water-surfaces. —Owing to the 
difficulty of duplicating conditions of humidity and temperature it is 
evident that determinations of evaporation from small shallow vessels 
are of little use in arriving at an estimate of the evaporation from large 
bodies of water. The best results have been obtained by the use of 
comparatively large vessels placed in a considerable body of water, 
such as a lake or reservoir. Even in this case the variation in tem¬ 
perature between the water outside and inside the vessel will at times 
be several degrees, and it is, moreover, difficult to eliminate the effect 
of the sides of the vessel in protecting the water-surface from the wind. 

52. Experiments at Boston .—The most extensive experiments of 
this character which have been made in the United States are those 
which were carried out by Desmond FitzGerald at the Chestnut Hill 
reservoir of the Boston water-works.* 

in Table No. 8 are given the mean monthly evaporations as de¬ 
duced from these experiments. For the summer months they are the 
means for ten years of observations, while for the winter months they 
are deduced from ‘special experiments on the evaporation from snow 
and ice. 

The maximum daily evaporation was 0.57 inch, the mean tempera¬ 
ture of the water being yo°.y F. in the reservoir and 68°. 8 in the tank. 
Experiments on snow and ice indicated an evaporation of about 0.02 


* See references (2) and (5), p. 63. 





54 


EVAPORATION AND PERCOLATION. 


inch per day from snow and 0.04 inch from ice. The maximum yearly 
evaporation was 43.63 inches and the minimum 34.05, or a variation 
of 11 per cent above and 13 per cent below the mean. 

TABLE NO. 8. 


MEAN MONTHLY EVAPORATIONS AT CHESTNUT HILL RESERVOIR, BOSTON, MASS. 


Month. 

Evaporation, 

Inches. 

Per cent of 
Yearly 
Evaporation. 

Month. 

Evaporation, 

Inches. 

Per cent of 
Yearly 
Evaporation. 


O 96 

2 • A 

July. 

5.98 

15-2 


T oc 

2 .7 

August. 

5-50 

I 4 .O 


1.70 

* J 

4- 

September. 

4 . T 2 

IO .4 


O . 07 

7 • 6 

October. 

3.16 

8.1 


A. a6 

11.4 

November.. . 

2 25 

5-7 

June. 

5.54 

14.2 

December . 

I.51 

3-9 


Total for the year = 39.20 inches. Mean temperature = 48°.6. 


53. Experiments at Rochester .—A similar series of experiments 
have been carried on since 1891 by Mr. Kuichling at the Mt. Hope 
reservoir of the Rochester water-works.* The results of these experi¬ 
ments are given in Table No. 9. They are the means of observations 
covering from two to eight years. 

TABLE NO. 9 . 

MEAN MONTHLY EVAPORATIONS AT MOUNT HOPE RESERVOIR, ROCHESTER, N. Y. 


Month. 

Evaporation, 

Inches. 

Per cent of 
Yearly 
Evaporation. 

Month. 

Evaporation. 

Inches. 

Per cent of 
Yearly 
Evaporation. 

January . 

February. 

March. 

April. 

May. 

June. 

O .52 

0-54 

1-33 

2.62 

3-93 

4.94 

1-5 
. 1.6 

3-9 

7.6 

11.4 
14-3 

July. 

August. 

September. 

October. 

November. 

December . 

5.47 

5 • 3° 

4-15 
3.16 
i-45 

1 • l 3 

15-8 

15-4 

12.0 

9.1 

4.2 

3-2 


Total for the year = 34-54 inches. Mean temperature = 47 0 .8. 


54. Other Experiments .—Experiments by J. J. R. Croes on the 
Croton River in 1865-1870 for eight to ten months of the year gave, 
as filled out by Mr. FitzGerald + for the winter months, an average 
annual evaporation of 39.64 inches. 

Of foreign experiments, those made by Mr. Charles Greaves at Lee 
Bridge, England, are probably the most extensive .X They embrace 
fourteen years of observations, and were carried out by means of a 

* See the various annual reports of the Executive Board of Rochester, N. Y. 

f Trans. Am. Soc. C. E., 1886, xv. p. 617. 

\ Proc. Inst. C. E., xlv. p. 19. 

































































CALCULA TED EVAPORA lTONS . 


55 


floating slate tank, 3 feet square and 12 inches deep, placed in the river 
Lee. The results are given in Table No. 10. The maximum yearly 
evaporation was 26.933 inches and the minimum 17.332, the variations 
being 31 per cent above and 16 per cent below the mean. 


TABLE NO. 10. 

MEAN MONTHLY EVAPORATIONS AT LEE BRIDGE, ENGLAND. 


Month. 

Evaporation, 

Inches. 

Per cent of 
Yearly 
Evaporation. 

Month. 

Evaporation, 

Inches. 

Per cent of 
Yearly 
Evaporation. 

January. 

February. 

March. 

April.. 

May . 

June. 

0.755 

0.603 

I.065 

2.098 

2-753 

3.I42 

3-6 

2.9 

5-2 

10.2 

13-4 

15-2 

July. 

August. 

September. 

October. 

November. 

December. 

3-443 

2.849 

1.606 

1.056 
0.669 
0.574 

16.7 

13-8 

7.8 

5-1 

3-3 

2.8 

% 


Total for the year = 20.613 inches. 


55. Calculated Evaporations from Water-surfaces. —In Table No. 11 
are given calculated evaporations deduced from readings of dry- and 
wet-bulb thermometers at various Signal Service stations in 1887 an( J 
1888, supplemented and controlled by observations at several stations 
by means of the Piche evaprometer.* The results indicate at least the 
relative conditions of temperature and humidity at the various stations, 
and are therefore indicative of the relative evaporation. They are 
believed by Mr. Russell, the officer in charge, to represent approxi¬ 
mately the evaporation from surfaces of ponds, lakes, and reservoirs. 
The results thus obtained for Boston, New York, and Rochester agree 
quite well with the observations already quoted. 

PERCOLATION, AND EVAPORATION FROM LAND-SURFACES. 

56. Influences Affecting Evaporation and Percolation. —Evaporation 
from the ground depends upon the moisture contained therein, upon 
the temperature, and upon the nature of the vegetation or other soil- 
covering. The moisture present in the ground depends in turn upon 
the rainfall, and the ability of the soil to receive and retain the perco¬ 
lating water. The greater the rainfall the greater the evaporation, but 
evaporation is relatively much more constant than the rainfall. It 
therefore follows that the difference, or the stream-flow, is more vari¬ 
able than either, and as the rainfall increases the percentage flowing 
off will increase. 


* Monthly Weather Review , Sept. 1888, p. 135. 

































56 


EVAPORATION AND PERCOLATION. 


TABLE NO. 11 . 


CALCULATED MONTHLY EVAPORATION IN THE UNITED STATES. 


Stations and Districts. 

Jan., 1888. 

Feb., 1888 

March, 

1888. 

April, 

1888. 

May, 

1888. 

June, 

1888. 

July, 

1887. 

August, 

3887. 

Sept., 

1887. 

October, 

1887. 

Nov., 

1887. 

Dec., 

1887. 

Year. 

1 

New England: 














Eastport. 

0.9 

1.4 

1-5 

2.4 

2-5 

2.7 

2.2 

2.9 

2-5 

2.6 

2. 2 

1.4 

25.2 

Portland. 

1.0 

1.2 

1.8 

2.6 

1.8 

3.3 

3-8 

3*9 

3-4 

3 *o 

2*5 

1.4 29.7 

Manchester. 

O. 9 

1.6 

2.2 

3-3 

3.8 

5 *o 

4.1 

3-3 

2.5 

2.8 

2.4 

i -4 33-3 

Northfield. 

0.8 

1.0 

i -5 

2-3 

2.5 

3-4 

3*5 

2.7 

2-3 

1.8 

I. I 

1.0 23.9 

B oston... • • •• • • •• • • • 

1.2 

1.6 

2.2 

3-4 

3 -i 

4-7 

4.4 

4.0 

3*5 

2.7 

2.2 

1.4 34*4 

Nantucket. 

1.1 

1.1 

1.2 

1-5 

i.S 

2.1 

3*3 

3*8 

3*4 

2-7 

1.8 

1.8 25.6 

Wood’s Holl. 

0-5 

0.8 

1.8 

2.4 

1.8 

2.7 

2.7 

2.4 

2.7 

1.2 

0.8 

0.5 

20.3 

Block Island. 

1.1 

1.1 

1.2 

2.0 

1.8 

2.6 

2-5 

3 *i 

2.8 

2.6 

1.8 

1.4 24.0 

New Haven. 

1.1 

1.6 

1.8 

2-7 

2.7 

4.1 

3-7 

3-8 

3 -i 

3*2 

2.4 

1.6 31.8 

New London. 

i -5 

1-3 

1-5 

2.6 

2.8 

4.0 

3*4 

3*9 

3*2 

3 *i 

2.4 

2.1 

31.8 

Middle Atlantic States: 













Albany. 

0.9 

1.2 

1.6 

3-3 

3-9 

4-5 

5 *o 

4-7 

3*2 

3 -o 

2.1 

1 .-4 

34-8 

New York City. 

1.8 

1.4 

2.0 

3-4 

3-3 

4.6 

5 *o 

5-2 

4-3 

4.1 

3-3 

2.2 

40.6 

Philadelphia. 

1.6 

2.1 

2-5 

4.4 

4.0 

5-7 

5*7 

5-2 

4*3 

4.0 

3*3 

2.2 45.0 

Atlantic City. 

1.2 

1.6 

i -5 

2.4 

1.8 

3 • 6 

2.9 

3*3 

2.4 

1.8 

1.2 

1*5 25.2 

Baltimore. 

2.0 

2.2 

2. S 

5-1 

4-7 

5-6 

6.0 

5 *o 

4*4 

4-3 

3*6 

2.4 48.1 

Washington City.... 

1.8 

i *7 

2-5 

4.2 

3-8 

6.0 

5*4 

4.9 

4.1 

4.2 

4*5 

2.5145.6 

Lynchburg. 

2.6 

2.7 

3-4 

5-2 

4-5 

5-6 

4*7 

4*3 

3*3 

3-4 

3*2 

2.6:45.5 

Norfolk. 

1.8 

1.6 

2-3 

3-5 

3-2 

4.2 

4.6 

3*7 

3 - 7 

2.9 

2*3 

1.8 

35-6 

South Atlantic States: 












Charlotte. 

2.6 

2.6 

4-3 

6.4 

4-5 

5-8 

4.0 

4.0 

4.6 

4.0 

3.6 

2.6 

49.0 

H atteras.•• • • • • •«••• 

1.8 

1.6 

1.6 

2.5 

2.2 

3 -o 

3-3 

4.1 

3*8 

3-2 

2.6 

1*631.3 

Raleigh. 

2.0 

1.8 

2.6 

3-8 

4.1 

5-4 

4.2 

3*2 

3 *o 

2.7 

2.4 

i* 8 l 37 .o 

Wilmington. 

2.4 

2.2 

2-7 

3-3 

3-3 

4-3 

4*3 

3 *i 

3-9 

3-4 

2.8 

2-7 

38.4 

Charleston. 

2.5 

2-5 

3-5 

3-7 

3-9 

4.4 

4*5 

4.8 

4.2 

4.0 

3*2 

2.5 43-7 

Columbia. 

2.2 

2-3 

2.6 

4. 8 

4-3 

5-4 

4.2 

3*8 

4.2 

3*4 

3*6 

2 - 44 V 2 

Augusta. 

3 -o 

2.6 

3-4 

5-3 

4.8 

5 -o 

4.8 

4-5 

5 *i 

4.1 

3*6 

3 -1 

40.3 

Savannah. 

3-3 

2.8 

4.1 

4-7 

4-3 

4.6 

4.2 

4-7 

3*4 

3*6 

3-5 

2.8 46.0 

Jacksonville. 

2.9 

2.6 

3-8 

4-3 

4.6 

5-3 

5-0 

4*7 

3-8 

3*6 

3 -o 

2.1 

45*7 

Florida Peninsula: 













Titusville. 

3-5 

2.6 

3-3 

3-8 

3-8 

4*3 

3*8 

4-3 

4.0 

4.1 

3*6 

3.1 

44-2 

Cedar Keys. 

3-3 

2.8 

4.0 

4.6 

4-5 

5 *i 

5 *o 

5-5 

4*5 

4.1 

3-5 

2.6 49. 5 

Key West. 

3-8 

3-7 

3-8 

4-5 

4.4 

4.8 

5 *i 

5 *i 

4*7 

4-3 

3*8 

3.651.6 

Eastern Gulf States: 














Atlanta.. .. 

2.7 

2.6 

4.0 

6.2 

4-7 

5-0 

4*5 

4*7 

5*8 

4.6 

4.2 

2.5 

51.5 

Pensacola. 

2.9 

2.8 

4.1 

4.0 

4-3 

4.6 

5-0 

5-4 

5-2 

4-5 

3*6 

2.448.8 

Mobile. 

2.6 

2.5 

2.8 

3-5 

3-7 

4.0 

4.1 

4.6 

4.6 

4.1 

3*4 

2.2 1 

42.1 

Montgomery. 

3 - 5 

3-3 

5 -i 

6.5 

5-9 

5*8 

4*3 

4-5 

5-7 

4.6 

4*3 

3 -i 

56.6 

Vicksburg. 

2.1 

2.5 

3-6 

5 -i 

5-7 

4.8 

40 

5*0 

4*7 

3*4 

4 -o ( 

2.2 

47 . I 

New Orleans. 

2.8 

2.8 

4.1 

3-8 

4.2 

4.1 

4.1 

4*3 

4.4 

4.6 

3 *7 

2 . 5 f 45.4 

Western Gulf States: 












1 


Shreveport. 

1.6 

2.1 

3 -o 

4.8 

4.9 

4.2 

4.9 

5-2 

5 -o 

4.1 

3.4 

2.4I45.6 

Fort Smith. 

2.2 

2.7 

3-5 

5-3 

4.4 

4.6 

5*6 

4.6 

4 * 7 

5-9 

3*9 

2.2 

49.6 

Little Rock. 

2.1 

2.8 

3-5 

5-5 

4 • 8 

4.1 

5*4 

5 9 

5-8 

5-2 

4.3! 

2.3 

51-7 

Corpus Christi. 

1.4 

1.6 

3-3 

3 -o 

3-2 

3*9 

4.4 

4-3 

4*3 

4.1 

3 *o 

2.3 

38.8 

Galveston. 

1.6 

2.8 

3-2 

2.9 

4-3 

4.2 

5*3 

5-2 

5*2 

4*7 

4.2 

2 . 4 , 46.0 

Palestine. 

2.1 

3-0 

3-3 

4.2 

4-3 

4*5 

5*8 

4.6 

4.8 

4*4 

4.0 

2. I 

47-1 

San Antonio. 

2.4 

3-3 

4.1 

3-8 

4.0 

4-5 

6.6 

5*8 

5-2 

5*4 

4.2 

3* 1 

52.4 















































































































CA L CULA TED E VAPOR A TIONS. 


5 7 


TABLE NO. 11 .— Continued . 


CALCULATED MONTHLY EVAPORATION IN THE UNITED STATES. 


Stations and Districts. 

Jan., 1888 

Feb.,1888 

March, 

1888. 

April, 

1 1888. 

Rio Grande Valley : 

Rio Grande City.... 

2.7 

3-5 

3-5 

3-6 

Brownsville. 

1.8 

2.6 

2.9 

3-0 

Ohio Valley and Ten¬ 
nessee : 




Chattanooga. 

2.0 

3.3 

3-3 

5-3 

Knoxville. 

2.4 

2.6 

3-4 

5 -o 

Memphis. 

2.1 

2.3 

3-1 

5-9 

Nashville. 

I.q 

2.1 

3.2 

5-9 

Louisville. 

1-7 

2.1 

2.8 

5-6 

Indianapolis. 

i -3 

1.4 

2.2 

4.6 

Cincinnati. 

1.8 

1.8 

2.6 

4.9 

Columbus. 

1.6 

2.0 

2.3 

4.5 

Pittsburg. 

1.4 

1.9 

2.2 

3-8 

Lower Lake Region : 





Buffalo. 

0.8 

1.1 

i -3 

2.2 

O s w c g o • • • • •••••••• 

0.6 

1.0 

1.1 

2.2 

Rochester •••••••••« 

o -5 

1.1 

0.9 

2.6 

Erlc************** •• 

1.0 

1.4 

1.4 

2.7 

( 3 icveland. • • • • • • • • •• 

1.1 

1.4 

1-5 

2.9 

Sandusky. 

0.8 

1.4 

i -5 

3-2 

Toledo. 

0.9 

1.1 

i -5 

3-5 

Detroit . 

0.8 

1.1 

1.6 

3 -o 

Upper Lake Region : 





Alpena. 

0.7 

0.6 

0.9 

1.6 

Grand Haven. 

0.5 

0.7 

i -3 

2.6 

Lansing •••• •••*•••• 

0.6 

1.2 

1.4 

2.7 

Marquette. 

0.8 

0.8 

0.9 

i -7 

Port Huron. 

0.6 

1.0 

1.1 

2.6 

Chicago. 

1.0 

I 2 

1.8 

3-2 

Milwaukee — . -. . . • 

0.5 

1.0 

1.1 

2.4 

Green Bay. 

0.5 

0.6 

0.8 

i -7 

Duluth. 

0.5 

0.5 

0.6 

i -5 

Extreme Northwest : 





Moorhead... 

0.2 

1.4 

0.5 

2.1 

Saint Vincent. 

0.3 

0.3 

0.5 

1.8 

Bismark. 

O.4 

0.6 

0.6 

3 -o 

Fort Buford. 

1.4 

0.7 

0.6 

3 -° 

Fort Totten. 

0.2 

0.3 

0.4 

2.2 

Upper Mississippi Val¬ 
ley: 





Saint Paul. 

0.7 

0.7 

2.2 

2.0 

La Crosse. 

O.4 

1.2 

1.4 

3-3 

Davenport. 

0-5 

1.0 

1.8 

3-8 

Des Moines. 

0.6 

1.0 

i -5 

3-7 

Dubuque. 

0.7 

1.0 

1.4 

2.2 

Keokuk. 

0.8 

1.1 

2.1 

4.2 

Cairo. 

1.6 

2.1 

2.9 

5-8 

Springfield, Ill. 

0.8 

1.1 

2.0 

4.6 

St. Louis. 

i -3 

1.6 

2-5 

1 5-5 


May, 

1888. 

June. 

1888. 

.'00 

>%00 

—> 

■*S 

uSS 

3 H 
< 

Sept., 

1887. 

October, 

1887. 

• CO 

> 00 

0 »- 

£ 

Dec., 

1887. 

Year. 

4-5 

4.6 

6.9 

7.0 

5-2 

4.9 

3-6 

3 -i 

53-1 

3-5 

3-9 

4.0 

4.1 

3-3 

3 -o 

2.6 

2-3 

37-0 

3-7 

4-3 

4-3 

5 -o 

5-4 

4.0 

3-9 

1.9 

46.4 

3-5 

4.2 

4.9 

5-0 

4.9 

4.1 

3-8 

2.1 

45-9 

5-3 

4.8 

4.9 

5-4 

5-5 

4.2 

4.1 

2.4 

50.0 

5 -o 

5 -i 

5-5 

6-3 

5 9 

4.0 

3 3 

1.9 

50.1 

5-4 

5-8 

6.8 

7.4 

64 

4.9 

3-8 

2.1 

54 8 

4 • 8 

5-7 

7-7 

6.9 

5-2 

4.1 

3 -i 

1.6 

48.6 

5-2 

6.4 

6-5 

6.6 

6.1 

4-7 

3-3 

2.1 

52 0 

4.8 

5-8 

6.9 

6.4 

5 -i 

4 0 

2.6 

1.8 

47.8 

4.2 

5-4 

6.6 

5-6 

4.9 

3-4 

2.8 

2-3 

44 5 

3*3 

3-9 

4.9 

5.2 

3-9 

2.8 

1.9 

1.6 

32 9 

2.8 

3-8 

3-9 

4.0 

3-6 

2.7 

2.2 

1.0 

28.9 

3-8 

4.9 

4.6 

4.1 

3-8 

2.6 

2.2 

i -3 

32.4 

3-7 

4.6 

5-5 

4.8 

3 -i 

2-5 

1.9 

1.2 

33-8 

3-3 

4.4 

5-2 

4.9 

3-8 

3-4 

2.4 

1.4 

35-7 

3-7 

4.6 

5-4 

5 4 

3-7 

3-4 

2.2 

i -3 

36.6 

3-8 

4.6 

6.0 

6.4 

3-7 

3-4 

2.4 

i -3 

38.6 

4.1 

48 

5-9 

5-2 

3-4 

2.8 

2.0 

i -3 

36.0 

2.1 

3-6 

3.8 

3-7 

2.8 

2.2 

1-5 

0.8 

24-3 

3 -i 

3-8 

4-7 

3-8 

2.7 

2.6 

i -7 

1.1 

28.6 

2.8 

4.0 

4-3 

3-9 

2.4 

1.9 

1.4 

1.0 

27 6 

2.4 

3-3 

3-4 

3-3 

3 -i 

2.2 

i -3 

i -3 

24-5 

3-0 

3-8 

4.6 

4.2 

3 2 

2-5 

t -7 

1.0 

29-3 

3-3 

4.8 

5-4 

5-3 

4-1 

3-2 

2.3 

1.2 

36.8 

2.6 

3-8 

4.8 

3-7 

3-4 

2.9 

1.9 

0.9 

29.0 

2-5 

4.1 

5-6 

4.2 

3 -o 

2.4 

1.9 

0.9 

28.2 

2.4 

2-5 

3-9 

3-4 

3 0 

2.5 

1.2 

1.0 

23.0 

3.6 

3-8 

3*7 

3-3 

3-5 

2.4 

1-3 

0.5 

26.3 

3-8 

3-9 

3 -t 

2.6 

2.6 

2.0 

0.9 

0.3 

22.1 

4-3 

4.1 

5-6 

4.2 

4.0 

2.6 

1.2 

0.4 

31.0 

4-7 

5 -o 

6.2 

4.9 

4.8 

3-0 

1-7 

0.5 

35-5 

4.6 

3-8 

4.2 

3 7 

3-7 

2.3 

1.4 

0.4 

27.2 

2-3 

4.1 

5 -o 

3-7 

2.8 

2.4 

i -5 

0.7 

28.1 

3 5 

4.4 

5-4 

4-7 

3 -o 

3 -o 

1.8 

0.8 

32.9 

3-4 

4.6 

6.9 

6.2 

4-4 

3 -o 

2-3 

1.1 

39 -o 

3 -i 

4.2 

6.6 

4-7 

4.1 

3-3 

2.3 

0.9 

56 0 

2.9 

4.2 

6.2 

4.8 

3-3 

2.8 

1.8 

0.9 

33-2 

3-7 

4-3 

7.0 

6.8 

5 -o 

3.8 

2.9 

1.2 

42.9 

4.4 

4-3 

5-6 

6-5 

5 -i 

-1- 5 

3.8 

2-3 

48.9 

3-8 

4-3 

5-4 

6-5 

4-5 

3-5 

2.9 

1.4 

40.8 

4-7 

5.0 

7-5 

8.0 

5-9 

4.9 

3-9 

1.4 

52.2 


































































































58 


EVAPORATION AND PERCOLATION. 


TABLE NO. 11 .— Continued . 

CALCULATED MONTHLY EVAPORATION IN THE UNITED STATES. 


Stations and Districts. 

Jan., 1888. 

00 

OO 

00 

M 

JO 

<D 

fa 

March, 

1888. 

April, 

1888. 

May, 

1888. 

June, 

1888. 

>^00 

August, 

1887. 

Sept., 

1887. 

October, 

1887. 

Nov., 

1887. 

Dec., 

1887. 

Year. 

Missouri Valley : 














Lamar. 

1.1 

1.6 

2.4 

4.4 

3-8 

4.0 

6.0 

4.6 

3-7 

3-6 

2.9 

1-5 

39-6 

Springfield, Mo. 

1.1 

i -7 

2.4 

5-0 

4-8 

4.0 

5 .o 

3-4 

3-4 

3-5 

3 -i 

1.4 

38.3 

Leavenworth. 

0.9 

i -5 

2.3 

4.6 

4-5 

5 -o 

6.3 

4-5 

4.0 

3-9 

2.7 

1.4 

41.6 

Topeka. 

1.1 

1.2 

2.0 

4.0 

4.1 

4.1 

6.3 

3-5 

3-2 

3 -o 

2.2 

1.4 

36.1 

Omaha. 

0.8 

i -5 

1.4 

4-4 

3-8 

5-2 

6.2 

5-2 

43 

1 4-3 

3-0 

1.4 

41.7 

Crete. 

0.7 

1.1 

1.2 

3-5 

3-3 

4.5 

5.6 

4-7 

3-8 

3-6 

2.4 

1.1 

35-5 

Valentine. 

1.2 

1.6 

1.8 

5 -o 

3-2 

5.3 

6.9 

5 -o 

5-2 

3-8 

3-3 

i -5 

43-8 

Fort Sully. 

0.6 

0.9 

i -3 

4 4 

4.1 

5-2 

7.7 

4.9 

5.7 

( 3.6 

2.8 

0.7 

41.9 

Huron. 

0.3 

0.7 

0.8 

3*7 

3-7 

4.1 

5-7 

4.2 

4.1 

3 - 1 

2.4 

0.7 

33 -o 

Yankton. 

Northern Slope : 

0.4 

1.4 

1.2 

3-3 

3 -i 

4.4 

4.6 

3-7 

2.9 

3 .o 

2.2 

0.8 

31.0 

Fort Assiniboine.... 

0.8 

1.2 

1.2 

3-8 

4.1 

4.2 

6.8 

5-5 

4.8 

3-5 

2-5 

1.1 

39-5 

Fort Custer. 

0.6 

1-5 

i -3 

5-4 

6.8 

4.9 

9.6 

8.0 

6.1 

3.4 

2.9 

1.5 

52.0 

Fort Maginnis. 

1.1 

1.4 

1.1 

3-3 

3-2 

4.6 

6.8 

4.6 

3.8 

2.8 

2.0 

1.1 

35-8 

Helena. 

1.1 

3-6 

2.1 

6.1 

4-3 

5-5 

7.2 

7-7 

6.4 

4 3 

3 -o 

2.1 

53-4 

Poplar River. 

0 4 

0.8 

0.8 

2.7 

4.9 

5-7 

6.0 

4.8 

4-4 

2-5 

i -7 

0.7 

35-4 

Cheyenne. 

3-3 

5-7 

4.0 

8.2 

5-2 

10.4 

8.0 

7-7 

8.6 

5*8 

6.1 

3-5 

76.5 

North Platte. 

0.8 

1.8 

1.8 

5-4 

3-9 

6.9 

6.0 

4.8 

3-7 

2.8 

2-3 

1.1 

4 i -3 

Middle Slope: 











Colorado Springs.... 

3 -o 

3-3 

4.1 

6.7 

5-6 

4-3 

6.7 

7.2 

6.8 

4.6 

4.2 

2.9 

59-4 

Denver. 

2.8 

3-7 

3-5 

7.6 

5-8 

10.5 

8.3 

8-5 

6.1 

4.9 

4.2 

3 -J 

69.0 

Pike’s Peak. 

2.1 

i -3 

i -5 

2.1 

1.8 

1.9 

3-0 

4.0 

3 -o 

2-3 

2.8 

1.0 

26.8 

Concordia. 

1.3 

2.8 

1.8 

4.8 

4-3 

5-7 

7-3 

5 2 

4-3 

4-5 

3-4 

1.8 

47-2 

Dodge City. 

1-4 

2.4 

2.8 

4.1 

4.6 

7-4 

8-3 

6.6 

5 5 

5-2 

4.2 

2.1 

54-6 

Fort Elliot. 

i -3 

1.9 

3-2 

5 -i 

5-4 

8.2 

7-6 

6.2 

5-4 

4-7 

4 2 

2.2 

55-4 

Southern Slope: 












• Fort Sill. 

1.6 

2.0 

2.6 

3-8 

4.0 

4.4 

4.8 

7-5 

5 -i 

4.2 

4.1 

2.0 

46.1 

Abilene •••••#••••••» 

1.8 

i -7 

3 -i 

4.2 

5.0 

5-8 

9-5 

7-5 

6.2 

4-5 

3-4 

i .7 

54-4 

Fort Davis. 

5-4 

5-7 

6.7 

8.5 

11.0 

12.0 

11.4 

9.0 

5-9 

5-2 

5-7 

4.9 

91.4 

Fort Stanton. 

3-9 

3-9 

5-2 

7-3 

9-5 

10.9 

9.4 

11.6 

3-9 

4.0 

3 6 

3-8 

76.0 

Southern Plateau : 










El Paso. 

4.0 

3-9 

6.0 

8.4 

10.7 

13 6 

9.4 

7-7 

5-6 

5-2 

4.6 

2.9 

82.c 

Santa Fe. 

3 -o 

3-4 

4.2 

6.8 

8.8 

12.9 

9.2 

9.8 

6.6 

6.7 

5-7 

2.7 

79.8 

Fort Apache. 

2.6 

3 -o 

3-6 

6.8 

9-4 

9.1 

7-1 

6.7 

5-3 

5-2 

4.1 

2.6 

65.5 

Fort Grant. 

5-2 

4.8 

6.4 

9.2 

10.2 

13.3 

12.4 

10.5 

9.0 

7-9 

7.2 

4.6 

101.2 

Prescott. 

1.4 

2.8 

3-6 

5-4 

6.2 

8.1 

6.6 

6.5 

4-7 

4.9 

3-6 

2.2 

56.0 

Y uma. 

4.4 

5-2 

6.6 

9.6 

9.6 

12.6 

11.0 

10.2 

8.2 

8.2 

^•5 

4.6 

95-7 

Keeler. 

3 -o 

4.6 

6-3 

8.7 

9-3 

11.9 

12.8 

13.9 

10.6 

8.8 

5-9 

4.8 

100.6 

Middle Plateau : 











Fort Bidwell. 

0.8 

1.8 

1.8 

4.6 

5-2 

4.0 

8.8 

8.1 

5-0 

4.6 

2.4 

i -3 

48.9 

Winnemucca. 

0.9 

2.8 

6.2 

9.1 

9-3 

10.1 

XI, 5 

12.0 

9.9 

6.6 

3-7 

1.8 

.83.9 

Salt Lake City. 

1.8 

2.7 

3-6 

7.2 

6.9 

8.9 

9.2 

10.7 

9.6 

6.5 

5-0 

2-3 

74-4 

Montrose. 

1.8 

2.7 

3 7 

6.2 

7.0 

11.1 

10.2 

8-3 

6.9 

5-2 

3-4 

2.0 

68.3 

Fort Bridger. 

1.6 

2.5 

2.7 

4-3 

4*3 

6-5 

7-7 

6.8 

5-6 

4.2 

5-2 

4-7 

56.1 

Northern Plateau: 








Bois6 City. 

1.6 

2-5 

3.8 

6.1 

6.5 

6.6 

10.0 

9.2 

7-4 

5-2 

3-2 

1.8 

639 

Spokane Falls. 

0.7 

i -7 

2.7 

4.4 

5-4 

4-4 

7-7 

6.4 

3-8 

2-5 

r -7 

1.4 

42.8 

Walla Walla. 

1.1 

2.9 

3.6 

6.2 

7.7 

5-7 

9.9 

7-9 

5 -i 

3-4 

1.8 

2.4 

57-7 























































































EFFECT OF VEGETATION OR CTHER SOIL - COVERING . 59 


TABLE NO. 11 . — Continued . 


CALCULATED MONTHLY EVAPORATION IN THE UNITED STATES. 


Stations and Districts. 


North Pacific Coast: 

Fort Canby. 

Olympia. 

Port Angeles. 

Tatoosh Island. 

A storia. 

Portland. 

Roseburg. 

Middle Pacific Coast: 

Red Bluff. 

Sacramento. 

San Francisco. 

South Pacific Coast: 

Fresno. 

Los Angeles. 

San Diego. 


Jan., 1888. 

00 

00 

00 

H 

£ 

March, 

1888. 

April, 

1888. 

May, 

1888. 

June, 

1888. 

a M 

August, 

1887. 

Sept., 

1887. 

October, 

1887. 

Nov., 

1887. 

Dec., 

1887. 

Year. 

1.2 

I. I 

1.8 

2 . I 

2.8 

2-3 

1.8 

2.9 

i. 8 

1.8 

1-5 

0.9 

21.1 

1-3 

1.2 

1.8 

2-5 

4-1 

3-3 

3-2 

3 -i 

2.4 

i -5 

i -3 

I. I 

26.8 

1.0 

0.9 

1.8 

1.8 

2-5 

2.1 

2.1 

1.8 

1-5 

1.2 

i -3 

1.1 

19.1 

I . 2 

I. I 

1.8 

1.4 

1.8 

1.8 

1.4 

1.4 

1.4 

1.6 

1.8 

1.4 

18.1 

I. I 

1.0 

1.6 

2.1 

3 -o 

2.7 

3 -o 

2.9 

2.6 

2-3 

1.8 

1.2 

25.3 

O.9 

I. I 

2.4 

3-4 

5-0 

3-2 

5-4 

4.2 

3-4 

2.7 

1.8 

1.2 

34-7 

1.2 

i .6 

2.7 

3-9 

4-7 

3-5 

5-4 

4-7 

5 -o 

3-2 

i -7 

1.6 

39-2 

3-0 

4.6 

5-4 

6.1 

7.0 

6.9 

11.0 

10.7 

10.1 

10.5 

5-9 

3-6 

84.8 

1.8 

3-1 

3-7 

4*3 

4.2 

5-6 

5-9 

5-6 

6-5 

7.3 

3-9 

2.4 

54-3 

2.7 

2.7 

3-3 

3 -i 

2.8 

3 -i 

2.4 

2-5 

3-3 

5 -o 

2.8 

3 -o 

36.7 

1.8 

2.8 

3-0 

5-6 

6.0 

7.0 

9.1 

10.2 

7.6 

6.7 

3-8 

2.2 

65.8 

2.3 

2.0 

2.8 

3-4 

3 -o 

3-8 

3-2 

3-5 

3 -J 

4.1 

3 -o 

3 -o 

37-2 

2.9 

2.7 

2-5 

2.7 

3-3 

2.8 

3-2 

3-3 

2.9 

4-3 

3-2 

3-7 

37 • S 


If the soil is very coarse or sandy, percolation will be rapid and 
large, and the water will soon escape beyond the reach of vegetation. 
This will result in a small evaporation, a large percolation, and conse¬ 
quently a large and steady stream-flow. If the soil is very fine, or is 
hard and impervious, both percolation and evaporation will be small and 
stream-flow large and irregular. Topography also greatly affects 
evaporation by affecting percolation. The maximum evaporation will 
occur where the soil is sufficiently porous and level to receive the water 
and to retain it within the reach of vegetation. 

57. Effect of Vegetation or Other Soil-covering. —As showing the in¬ 
fluence of vegetation on evaporation, Risler’s widely quoted table of 
the daily consumption of water by various crops during the growing 
season is here given: 

P . Consumption of Water 

'-' ro P* in Inches per Day. 


Meadow-grass 

Oats. 

Indian corn... 
Clover .., 

Vineyard. 

Wheat. 

Rye. 

Potatoes. 

Oak trees. 

Fir trees. 


0.134 to 0.267 
0.140 “ 0.193 
0.110 “ 0.157 

0.140 “ . 

0.035 “ 0.031 
0.106 “ o.iic 

0.091 “ . 

0.038 “ 0.055 
0.038 “ 0.035 
0.020 “ 0.043 


These figures indicate that the grain crops will consume from 10 to 
15 inches of water during the growing season. Grasses requite still 
more per day, and for an entire summer season will consume 30 or 40 































































6o 


evaporation and percolation . 


inches, if furnished. Baldwin Latham found that Italian rye-grass 
would under suitable conditions consume from ioo to 200 inches per 
year, if supplied.* 

From this it is seen that the demands of vegetation during the 
growing season are very great, and until these are satisfied very little 
is left to replenish the ground-water or to add to stream-flow. The 
large amount consumed by grasses and grains as compared to forest 
trees is to be noted. Other experiments indicate less difference in 
favor of forest trees, but there is little doubt that forests require less 
water than crops. Fernow gives as the ratios of the evaporation from 
different surfaces relative to that from a water-surface the following: 
sod 1.92; cereals 1.73; forest 1.51; mixed 1.44; water 1.00; bare 
soil o.6o.t Forests not only consume less water than crops, but, what 
is of more importance, they promote regularity of stream-flow by 
retarding the surface-flow and so increasing the percolation as well as 
delaying and decreasing the flood-flow. 

The effect of a covering on the ground-surface is shown by experi¬ 
ments of Eser. Calling the evaporation from bare ground 100 per 
cent, the evaporation from ground covered with 1 cm. of sand was 
33 per cent; when covered with 5 cm. of straw 10 per cent; with 
5 cm. of forest leaves from 11 to 15 per cent; and with grass growing 
thereon 243 per cent.J 

The effect of vegetation, or other covering, upon the percolation is 
of course the reverse of its effect upon evaporation. Experiments by 
Wollny on bare soils 20 inches deep showed that for six months, May 
to October, the percolation was, for sand 65 per cent, for loam 33 per 
cent, and for peat 44 per cent of the rainfall. With grass growing 
thereon the percolation was 14.0, 1.3, and 8.7 per cent, respectively, 
nearly all of which occurred in October.§ 

58. Experiments on Evaporation and Percolation.—Greaves carried 
out in connection with his experiments quoted on page 55 many experi¬ 
ments on soils. Two slate tanks were filled, one with ordinary soil 
and sodded over, the other with fine sand. All the rain either evap¬ 
orated, or percolated through the soil. The average results for 
fourteen years were as follows: 


Soil. 


Sand. 


Rainfall.... 
Percolation. 
Evaporation 


25.72 inches 
7-53 “ 

18.14 “ 


25.72 inches 
21.41 “ 


4.31 


§ Ibid ., p. 38. 


* Proc. Inst. C. E., lxxiii. p. 236. 
f Bulletin No. 7, Forestry Div., Dept. Agriculture. 

X Handbuch der Ingenieurvvissenschaften; Der Wasserbau, 1. Abt., 1. Halfte d. q a 

K This/ nQ ' r’ <5*r 








EXPERIMENTS ON EVA PORATION AND PERCOLATION . 61 


Experiments with uncropped soils 5 feet deep by Gilbert and Laws 
at Rothamsted, England, from 1870 to 1890, gave the average results 
shown in Table No. 12. The average percolation through 40 inches 
of soil was 15.16 inches, and through 20 inches was 14.38 inches. 
The evaporation was much more uniform than the percolation, it vary¬ 
ing from 11.89 t° 21.74 inches, while the percolation varied from 3.94 
to 24.38 inches. The soil was of a rather heavy character. The areas 
were T¥ Vo acre i n extent, inclosed by cast-iron boxes, and the drainage- 
water was collected and measured.* 


TABLE NO. 12 . 

EVAPORATION EXPERIMENTS AT ROTHAMSTED, ENGLAND. 


Month/ 

Rainfall. 

Inches. 

Evaporation. 

Inches. 

Percolation. 

Inches. 

Month. 

Rainfall. 

Inches. 

Evaporation. 

Inches. 

Percolation. 

Inches. 

January . 

February . 

March. 

April. 

May. 

June. 

2.51 
2.04 
I.74 
2.21 
2.28 

2.52 

0.45 

O. 60 
0.88 
i -53 
1.69 
1.92 

2.06 

I.44 

0.86 

0.68 

0-59 

0.60 

July. 

August. 

September. 

October. 

November. 

December. 

3-03 

2.45 

2.86 

3-20 

3-03 

2.42 

2.26 

1-95 

2 . II 

I . 70 

0.98 
0.61 

O.77 
O. 50 
0-75 
1.50 
2.05 

I.8 l 


Average yearly rainfall. 30.29 inches. 

“ “ evaporation. 16.68 “ 

“ “ percolation. 13.61 “ 


Average yearly rainfall. 30.29 inches. 

“ “ evaporation. 16.68 “ 

“ “ percolation. 13.61 “ 


In Table No. 1 3T are given the results of various European experi¬ 
ments on percolation through various depths of soil and under various 
conditions. The data are of value as indicating the relative percola¬ 
tions under different conditions. The actual figures must, however, be 
used with caution, as in most if not all cases the experiments were so 
conducted that all the precipitation either percolated or evaporated. 
In actual drainage-areas a portion reaches the stream by running over 
the surface, most of the flood-flow being thus derived. 

59. Evaporation as Determined from Stream-flow.—The average 
evaporation from large areas as determined by subtracting stream-flow 
from rainfall can be readily obtained for several watersheds from the 
data given in Chapter VI. Within the range covered by the data, the 
mean annual evaporation for the Atlantic coast region obtained in this 
way is given approximately by the formula E = 12 \R, where 

E — annual evaporation, and R — annual rainfall in inches. Vermeule 
suggests as a general formula A = (15.50-f- .\ 6 R)(.o$I — 1.48), in 
which T — mean annual temperature in degrees Fahrenheit. £ 

* Proc. Inst. C. E., cv. p. 31. 

f From Lueger. Die Wasserversorgung der Stadte, p. 203. 

\ Geolog. Survey N. J., 1894, ill. p. 76. 







































62 


EVAPORATION AND PERCOLATION. 


» 


TABLE NO. 13 . 

EXPERIMENTS ON PERCOLATION (LUEGER). 


Place. 


Abbotshill. 

Holmfield. 

Lee-Bridge .... 

- < 4 

• • • • 

Rothamsted. .. 

Caleves. 

Gorlitz. 


Tharand > 
Moholz \ 
Erlangen. 

Salzburg. 

< 4 

Oberdobling.... 


c 


With or 


c n 

Kind of Soil. 

Without 

c 

og 

Vegeta- 

— <u 

jz-a 


tion. 

< 2-5 

«-» O 

c 



.5 a 

Q ' 




36 

Sandy loam 

With 

26.0 

36 

Dolomitic soil 

With 

24.7 

36 

Sand 

Without 

25-7 

36 

Loamy sand 

With 

25-7 

40 

Loam and clay 

Without 

31.0 

47 

Clay 

With 

39 -S 

49 

Clay 

Without 

25-7 

49 

Loam 

Without 

25.7 

49 

Sandy loam 

Without 

25-7 

49 

Clay 

With 

29.0 

49 

25 

25 

Loam 

Sand 

j Sandy loam ) 

) and clay f 

With 

Without 

With 

29.0 

30.2 

25 

>lar._yloam ) 

} and clay f 

Without 

30.2 

50 

Loam 

Without 

25-8 


Percolation in per cent of Rainfall. 


Spring. 

Summer. 

Fall. 

Winter. 

Year, 

30-3 

24.9 

1-7 

7-7 

54-1 

22.8 

83.9 

30.3 

42-3 

19.6 
83.2 

26.6 









43-4 
28.0 





36.1 

52.4 

49-7 

59 -° 

89.7 

29-3 

45-6 

42.4 

21.3 

36.0 

26.5 

28.6 

27.9 
20-9 

32.9 

19.O 

29.9 

37-7 

8 - 1-4 

92.0 

28.1 
41.0 
40-5 
40.8 

58.7 
43-0 

33-9 

64.2 

32.8 









43-3 

41.0 

24.4 

32.0 


6 o. Amount of Percolation over Large Areas. —The proportion of the 
stream-flow that is derived from the ground-water or from the percola¬ 
tion varies greatly for different watersheds. Even where the subsoil 
is very porous it is usually the case that the surface-soil is more or less 
clayey and during heavy rains much water will flow off over the sur¬ 
face. Long Island furnishes an example of conditions very favorable 
to percolation, the amount obtained directly from wells at Brooklyn 
being in 1894 two-thirds of the total yield of the watersheds drawn 
from. This is equivalent to about 500,000 gallons per day per square 
mile, equal to 10.5 inches or 28.5 per cent of the rainfall. The total 
percolation must have been at least 12 inches, or three-fourths the total 
yield. Experience in Holland in collecting water from sand-dunes 
indicates that from 30 to 50 per cent of the rainfall is available in the 
ground-water. Conditions are, however, seldom so favorable as at 
these places. 

An approximate estimate of the total amount of percolation which 
is useful in adding to stream-flow or to ground-water supplies may be 
made for any particular region by subtracting the flood-flows of a stream 
from its total flow, providing the storage afforded by small ponds and 
lakes is insignificant. In small streams the flood-flows increase and 















































PERCOLATION OVER LARGE AREAS. 


65 

decrease so rapidly that it is not difficult to eliminate in this way most 
of the surface-flow. 

The results of an analysis of this kind of the daily flow of the 
Perkiomen, Neshaminy, and Tohickon, made from data given in the 
reports of the Philadelphia Water Bureau, show that the annual run-off, 
excluding the flood-flows, usually amounts to from 5 to 8 inches. This- 
is equivalent to from 25 to 35 per cent of the total run-off and 12 to 18 
per cent of the rainfall. 

LITERATURE. 

1. Greaves. On Evaporation and on Percolation. Proc. Inst. C. E. r 

1 875—76, xlv. p. 19. 

2. FitzGerald. Evaporation. Trans. Am. Soc. C. E., 1886, xv. p. 581. 

Contains results of experiments at Chestnut Hill Reservoir, Boston, 
together with many others made to determine the laws of evapora¬ 
tion, and a full discussion of the entire subject. 

3. Depth of Evaporation in the United States. Monthly Weather Review y 

September, 1888. 

4. Harrison. On the Subterranean Water in the Chalk Formation of the 

Upper Thames and its Relation to the Supply of London. Proc. 
Inst. C. E., 1890-91, cv. p. 2. 

5. FitzGerald. Rainfall, Flow of Streams, and Storage. Trans. Am. Soc. 

C. E., 1892, xxvii. p. 253. 

6. Fernow. Relation of Evaporation to Forests. Bull. No. 7, Forestry 

Div., U. S. Dept. Agr. Eng. News , 1893, xxx. p. 239. 

7. Vermeule. Report on Water-supply. Geological Survey of New Jersey, 

1894, hi. A valuable and exhaustive discussion of the subject of 
rainfall, evaporation, ground-storage, and stream-flow as applied to 
New Jersey. 

8 . Handbuch der Ingenieurwissenschaften, Band 111, Abt. 1, 1. Halfte, and 

Lueger, Wasserversorgung der Stadte, contain many references to 
the foreign literature of this subject. 






CHAPTER VI. 


FLOW OF STREAMS. 

61. General Methods of Procedure.—When a stream is under con¬ 
sideration as a source of water-supply, the peculiarities of its flow—the 
minimum, maximum, and total flow for various periods of time—are 
among the first things to be determined. The most accurate as well 
as the most direct method of determining these is by means of a series 
of gaugings extending over several years, which, to be of the greatest 
value, should include periods of high flood and periods of drought. A 
long series of gaugings is, however, seldom available at the time when 
a source must be decided upon, but by establishing gauges at the 
earliest possible moment much valuable information may be had by the 
time detailed designs are required. This applies especially to the case 
of a city seeking an additional supply. 

Where gaugings are not to be had, or where they are very limited 
in extent, as close an estimate as possible must be made from a com¬ 
parison with other streams whose flows are known, taking into account 
as far as may be the differences in rainfall, climate, and in the various 
characteristics of the different watersheds. Where such differences are 
great this method will give results only roughly approximate, but still 
much better than mere guesses and quite sufficient in many cases to 
determine the availability of a given source. Where, however, the 
margin is close, and in problems pertaining to the detailed design, a 
more accurate knowledge is greatly to be desired. It can be obtained 
only by means of gaugings. 

62. Influences Affecting Stream-flow.—All streams derive their 
supply ultimately from the rainfall, and, in general, the amount of the 
run-off is equal to the rainfall less the evaporation. In the last chapter 
the various influences affecting evaporation and percolation were dis¬ 
cussed, and it only remains to consider how the variations in these 
factors go to affect stream-flow. 

Whatever augments evaporation decreases stream-flow, and by the 

64 



if NITS OF MEASURE. 


65 


same amount. Thus a watershed with a large percentage in grass will 
yield a less amount than one with rocky and barren hillsides; one with 
a large percentage of water-surface, less than one with a small per¬ 
centage. Again, the higher the temperature the greater the evaporation 
and the less the stream-flow. An increased rainfall will also increase 
the evaporation, but the relative increase in evaporation will be less than 
that in the rainfall; hence the larger the rainfall the greater the per¬ 
centage flowing off. The distribution of the rainfall throughout the 
year also affects greatly the evaporation and consequently the stream- 
flow. 

The effect of large percolation is to make the run-off more uniform; 
but where the water is held for the use of vegetation by a porous soil, 
a large percolation may result in a decreased total flow. Steep, rocky 
hillsides will give a large per cent of the rainfall to the streams, but the 
flow will be very irregular; flat grass-lands will give little or nothing 
to the streams during the season of growth. Again, the winter climate 
has, through its effect on percolation, an important influence on the 
regularity of the flow. When the ground is frozen, little water goes 
to replenish the ground-storage during the melting of the snow, but if 
the soil is open to winter rains and snows, much water will be furnished 
through percolation to increase the summer flow, while the spring floods 
will be correspondingly reduced. This effect of climate is well illus¬ 
trated in Fig. 15, page 78, in the curves for the Connecticut and 
Savannah rivers. 

It is thus seen that temperature, topography, vegetation, and soil, 
as well as the amount of rainfall, are important factors to be considered 
in a study of the flow of a stream. 

It should here be noted thai from any given area of watershed a 
portion of the percolating water is likely to escape to a lower point of 
the valley before coming to the surface. The amount lost in this way, 
although usually insignificant, is sometimes very large. This question, 
together with methods of utilizing such water, is discussed in subsequent 
chapters; for the present it will be assumed that this portion is so small 
in amount that it may be neglected. 

63. Units of Measure.—Rainfall is expressed in inches in depth, and 
the rate in inches per hour or per twenty-four hours; and for compara¬ 
tive purposes stream-flow is often likewise expressed, meaning thereby 
inches in depth over the entire watershed. For other purposes the 
flow is usually expressed in cubic feet, or cubic feet per square mile of 
watershed, and the rate of flow in cubic feet per second, or cubic feet 
per second per square mile. The foot and second units are also con- 


66 


FLO W OF STREAMS. 


venient to use in all hydraulic formulas, but in matters pertaining to 
storage and distribution the gallon unit is in common use, and rates 
are expressed in gallons per minute and gallons per twenty-four hours. 

For convenience in computations relative to rainfall and flow of 
streams, the following table is inserted. 

TABLE NO. 14 . 


VOLUMES AND RATES OF FLOW IN FEET AND SECONDS CORRESPONDING TO GIVEN 
VOLUMES AND RATES OF RAINFALL IN INCHES AND HOURS. 


Depth in 
Inches. 

Cubic Feet per 
Square Mile. 

Inches per 
Hour. 

Cubic Feet per 
Second per Square 
Mile. 

Inches per 

24 Hours. 

Cubic Feet per 
Second per Square 
Mile. 

0 . I 

232,320 

0.1 

64.5 

I 

t 

26.9 

O. 2 

464,640 

O. 2 

129.O 

2 

53-8 

0-3 

696,960 

0.3 

193-5 

3 

80.7 

O.4 

929,280 

0.4 

258.1 

4 

107-5 

0-5 

1,161,600 

0-5 

322.6 

5 

134-4 

0.6 

1,393,920 

0.6 

387-1 

6 

161.3 

0.7 

1,626,240 

0.7 

451-7 

7 

188.2 

0.8 

1,858,560 

0.8 

516.2 

8 

215-1 

0.9 

2,090,880 

0.9 

580.7 

9 

242.0 

1.0 

2,323,200 

1.0 

645-3 

10 

268.9 


One inch of rain = 2,323,200 cu. ft. per sq. mile. 

One inch per hour = 645.33 cu. ft. per sec. per sq. mile. 

One inch per 24 hours = 26.89 cu - ft. per sec. per sq. mile. 

One cubic foot = 7.4805 U. S. gallons. 

One cubic foot per sec. = 646,300 gallons per day. 

64. Divisions of the Subject—The question of the flow of streams 
naturally divides itself into three parts: 

First, the minimum flow of the stream. 

Second, the maximum or flood flow. 

Third, variations in the flow through successive months and years. 

The first information is necessary in case a stream is under consid¬ 
eration for which but little storage is obtainable, or in answer to the 
question whether it is practicable to draw directly from the stream 
without storage. The second is of great importance in the design and 
execution of all river work, and especially in determining the size of 
waste-weirs. The third determines the supplying capacity of the water¬ 
shed and the size of impounding reservoirs. 

MINIMUM FLOW. 

65. The dry-weather flow of streams is maintained entirely from 
ground- and surface-storage; and as facilities for such storage vary in 



















MAXIMUM FLOW. 


67 


different watersheds, so will the minimum flow vary. Surface-storage, 
if consisting of large areas of shallow lakes and ponds, acts to decrease 
greatly the total flow of a stream on account of the great evaporation, 
while at the same time it usually increases the minimum flow. 

In Table No. 1 5 on page 68 are given the minimum flows of several 
streams in different localities. For streams in the northern Atlantic- 
coast States these and other statistics indicate that for watersheds of less 
than 200 square miles in area the minimum flow varies from nearly 
zero to about 0.2 cubic foot per second per square mile, averaging o. 10 
or 0.12. For large streams the minimum is rarely less than o. 10, and 
in some cases is as high as 0.30, the latter figure being about the mini¬ 
mum flow for the Connecticut with an area of 10,234 square miles, and 
for the Merrimack with 4599 square miles of watershed. In the upper 
Mississippi valley the minimum flow is much less, as indicated by the 
data for the Rock, the Illinois, and the Des Plaines rivers. Streams 
in this locality of several hundred square miles of watershed are likely 
to have a minimum of zero, while still further west this applies to 
streams of thousands of square miles of catchment-area. 

MAXIMUM OR FLOOD FLOW. 

66 . General Considerations. —The maximum rate at which the waters 
from great storms will pass down a stream is affected largely by the 
steepness of the slopes, by the size and shape of the drainage-area, and 
by the distribution of the branches. Small areas will have larger 
maximum rates of flow than large areas, other things being equal, as 
the former are affected by short rainfalls of high rates, while in the 
latter case the maximum flows are caused by rains of longer duration 
but of less intensity. For a like reason streams with steep slopes will 
have a higher maximum rate than those with flat slopes. 

The evaporation which takes place during a flood is of so little 
importance that its effect may be neglected. Percolation absorbs large 
portions of heavy rains if the ground is dry, but such rains are quite as 
apt to occur with the ground already soaked or even frozen, so that in 
the extreme case, which is the one that must be considered, percolation 
is of small moment. 

Of much greater importance in distributing the run-off over a long 
interval of time, and so reducing the maximum rate, is the surface 
storage of natural lakes and ponds and of those created by the inunda¬ 
tion of large flats bordering the stream. The effect of this last factor 
may be sufficient to reduce the flood-flow to one-half or one-fourth that 
of a stream with a narrow valley. 




63 


FLO IV OF STREAMS . 


67. Data of Maximum Rates of Flow. —In Table No. 15 are given 

data concerning the maximum flows of several streams, and, where 
possible, the approximate amount of rainfall producing the maximum 
flow. A great variation is observable in the table, due partly to the 
varying rates of rainfall, but largely to the differing characteristics of 
the streams. Nevertheless the data will be of some assistance in 
estimating probable maximum floods. 

TABLE NO. 15 . 


MINIMUM AND MAXIMUM FLOW OF STREAMS. 




_r c/5 

U-- 

aT&s 

° w 4 . 

0 



Stream. 

Place. 

u 'ZZ 

ft V 
on u 
re rt 
c 3 

E k* fc 
a 0 a 
£5 0 

. s -e 0 

Rainfall at Time of 
Maximum Flow. 

Authority.* 



g«Sf 

•2 3 V 

■Sum 

x r z v 
ajUc n 





Q 

S 

s 

t 



New England. 






Merrimack 

Lawrence 1 

4.599 

10,234 

3.287 

352 

190 

109 

0.31 
0.51 
0.306 
0.17 

20.87 

20.27 


(II) 

(1) 

(3) 

(1) 

(2) 

(2) 

■> 

Connecticut 

Hartford 


( ( 

Dartmouth 


Concord 

Lowell 

12.64 

56.85 

104.5 


Pa wtuxet 

Rhode Island 


Nashua 

Massachusetts 




' About 6.6 in. of 






rain and snow. 


Sudbury 

44 

78 

0.036 

44.2 

Maximum in 24 

K11). ( 5 ) 






| hours about 3 







f inches. 


Flat River 

Rhode Island 

61 


120.75 

J (2) 

New York. 




Chemung 

Elmira 

2,055 


67.1 

j From 6 to 10 in. 

1 (14) 

0.150 
0.016 

( in 24 hours. 

Croton 


339 

20.37 

6,790 

879 

74.87 

54.43 

(11), (2) 
(2) 

Croton West Br. 



New Jersey. 


Delaware 

Stockton 

0.17 
0.20 

37.5 

68 


(11) 

(11). (12) 

(12) 

(11) 

(11), (12) 

Raritan 

Bound Brook 


Passaic 

Dundee 

822 


22 

About 3.7 in. of 

« < 

Paterson 

772.9 

0.19 
0.17 

Pequest 

158 

13 

1 rain with 0.6 
j in. of snow in 

Paulinskill 


126 

0.13 

54 

< 1 ii 

Pequannock 


48 

115 

24 hours. 

(12) 




South Branch 


276 

159-5 


100 

66. 1 

J 

i 4 

Ramapo 

Pompton 

Pennsylvania. 

0.14 

(II) 


Ohio 

Pittsburgh 

Philadelphia 

19,900 

0.114 

0.210 



( 3 ) 

(2) 

Schuylkill 

i,Soo 




( About 3.5 in., of 

Perkiomen 

Frederick 

152 

0-39 

34-9 

- which 2.7 in. 

( fell in 24 hrs. 

[ (18) 

Neshaminy 

Forks 

139-3 

0.009 

41.4 

14 

f About 3.8 in. in 

] 

Tohickon 

Point Pleasant 

102.2 

0.002 

54-3 

J 3 da., of which 

1 1.7 in. fell in 

I 

y “ 






L 24 hours. 

j 


* See references on p. 83. 




















































MAXIMUM FLOW. 


69 


TABLE NO. 15 .— Continued . 


MINIMUM AND MAXIMUM FLOW OF STREAMS. 


Stream. 


South Fork 


Potomac 


«c 
i i 


Rock Creek 

i i 4 4 


Illinois 

Rock 

Des Plaines 


Place. 


Dam in Croyle 
Township 


Maryland. 
Great Falls 
Dam No. 5 
Cumberland 
Georgetown.D.C. 
Hoyle’s Mill,D.C, 

Illinois. 

Mouth 

Rockford 

Riverside 


_r 75 
oS 

?a 

bill! 

rt rt 
c 3 

Q 


48.6 


11,043 

4,640 

1,364 

77-5 

64.4 

27,800 

6,500 

630 


u •— 

£ XS 
o - cr 

a^ u 
30a 
85 


■a 3 


.-Uts) 

s 


0.078 

0.018 


o. 114 


0.043 


o 


Maximum Flow, 

Cubic Feet per 

Sec. per Sq. Mi. 

Rainfall at Time of 
Maximum Flow. 

215 

42.5 

20 

131 

126.4 

’ From 6 to 8 in. 

in 2 days. For 
, several hours 
’1 the rate was 
about f in. per 
f hour. 







. 


. 

21.4 




Authority.* 


f (6) 


(i 3 «> 

( 3 ) 


4 4 
4 4 


(130 

4 4 

( 15 ) 


* See references on p. 83. 


68 . Formulas for Flood-flows. —Various formulas have been proposed 
for expressing the maximum flow of a stream, some involving only the 
rainfall and area, while others attempt to take account also of the slope 
and shape of the watershed. Obviously any formula which does not 
involve the last two factors is not of general application, although it 
may give good results for a particular class of streams. In applying 
such a formula to other streams due allowance must be made for the 
differing conditions. 

Among the most widely known of this class of formulas is that 
given by Fanning and recommended by him as applicable to average 
New England and Middle-State basins. It is 

Q= 20 °jtf> •••••••(!> 


in which Q = discharge in cubic feet per second per square mile, and 
M _ area j n square miles. Thus the total discharge is made to vary 
according to M*. The discharges given by this formula have been 
materially exceeded in some cases, especially for the smaller water¬ 
sheds, and have been reached by floods caused by rains much below 
the maximum. It gives a value of Q which appears to increase some¬ 
what too slowly with decrease in area. 










































70 


FLOW OF STREAMS. 


Another formula derived from measurements of streams of flat 
slopes in the upper Mississippi valley is that proposed by Cooley * and 
is 

M 1 

Q = i8o ~m .( 2 ) 

It is intended to represent those floods occurring with comparative fre¬ 
quency, as once in six or ten years. Several other formulas are given 
by Mr. Cooley in the paper referred to. 

It may be here noted that the waste-weirs of the dams of the 
Boston Water-works are designed to carry a flood-volume at the rate 
of 6 inches per 24 hours, or 161 cubic feet per second per square mile. 
The watersheds are from 20 to 75 square miles in area. 

69. Rational Method of Estimating Flood-flow.—A more rational 
method than by the use of a formula, and one which is applicable to 
any area, has been proposed by some engineers, most recently by 
Mr. Chamier in a paper before the Institution of Civil Engineers. + It 
is based upon the following principles: 

Assuming a uniform rate of rainfall, the flow of a stream will 
increase rapidly until a sufficient time has elapsed for water to reach 
the point in question from all parts of the drainage-area. After this, 
with a continuation of the rain, the increase in flow will be much 
slower, being now due to the increase in the percentage flowing off. 
The maximum flood will then probably be produced by the greatest 
possible rainfall of a duration corresponding to the length of time above 
mentioned. Rates of rainfall of long duration are far from uniform, but 
irregularity in the rate within the time required for the concentration 
of the water to the point of discharge will have little effect on the 
maximum rate of flow. 

The elements to be determined in this method are then: (1) the 
length of time required for the water from the most remote part of the 
watershed to reach the point of discharge; (2) the maximum rate of 
rainfall of a duration equal to this time; and (3) the percentage flowing 
off. The maximum rate of flow will then be equal to this rate of rain¬ 
fall multiplied by the percentage as above found. 

(1) The Time Required. —In estimating this time the maximum 
distance to be covered can be obtained from a good map of the area 
in question, making due allowance for the sinuosities of the smaller 
channels. The velocities of flow are more difficult of estimation. In 

* Jour . West . Soc . Engrs ., 1896, 1. p. 306. 

f Proc. Inst. C. E., 1898, cxxxiv. p. 313. Abstracted in Engineering Record , 1899, 
XXXIX. p. 163. 







MAXIMUM FLOW. 


71 


channels of considerable size they may be roughly estimated by 
Kutter’s formula, the slopes and high-water cross-sections being 
known. For smaller branches the velocity will usually range from 
two to four miles per hour, though in some cases it may be consider¬ 
ably higher. On lateral slopes, before reaching well-defined channels, 
the water will move at a slow velocity, estimated by Mr. Chamier at 
from one-half to one mile per hour. In any case • an approximate 
estimate of velocity in the various channels can be made by a few direct 
observations during moderately high water. 

A good notion of the total time required for the concentration of 
the water may also be obtained by observing the-time which elapses 
from the beginning of a sudden storm until the maximum effect is felt 
at the point of discharge. Where the country is level and the drainage- 
channels far apart, or where there is large surface storage, this would 
be the most reliable method of estimating the time. 

If the element of time is correctly determined, the effects of size 
and shape of area, of slopes, and of surface storage will all have been 
taken account of to a very large degree. 

(2) The Rate of Rainfall .—The time having been determined, the 
corresponding rainfall may be taken from the data of the last chapter. 
To the estimated rainfall, if occurring in the winter, may be added a 
maximum of about 2 inches for melting snow. 

(3) The Percentage Flowing Off .—The total flood-discharge of a 
stream at times when the ground is previously soaked or frozen will 
usually vary from 50 to 75 per cent of the rainfall. The percentage 
running off during the rise of a stream will, however, be considerably 
less than the total percentage for the entire flood, on account of the 
effect of pondage and the greater percolation during the first part of the 
storm. In the paper already referred to Mr. Chamier estimates the 
percentages for different conditions as follows: 

For flat country, sandy soil, or cultivated land, 25 to 35 per cent. 

For meadows and gentle declivities, absorbent ground, 35 to 45 
per cent. 

For wooded hill-slopes and compact or stony ground, 45 to 55 P er 
cent. 

For mountainous and rocky country or non-absorbent surfaces, as 
frozen ground, 55 to 65 per cent. 

70. Diagram for Flood-flows.—The diagram Fig. 13 gives directly 
the rate of flood-flow corresponding to various percentages and various 
values of the time required for the concentration of the flood-waters as 
determined under (1). It is constructed on the basis of rainfalls 


72 


FLOW OF STREAMS. 


according to the middle curve of Fig. 12, page 49, or the lower curve 
with 2 inches added for snow. For small areas in which the maximum 
flow is normally reached-in three or four hours, an allowance of 1 inch 
for snow would be sufficient. 

In making use of this diagram it should be remembered that it is 
based on very excessive and rare rainfalls, and therefore the flood-flows 



Fig. 13.—Flood-volumes. 


resulting will be the extraordinary floods which may occur perhaps once 
or twice in a century. Such, however, must be provided for in design¬ 
ing waste-weirs where inadequate dimensions would endanger the lives 
of the population in the valley below. For structures where a failure 
would mean a property loss only, it would often be more economical 
to provide for ordinary floods only, in which case a less rate of rainfall 
should be adopted according to local conditions. 

71. Example. —To illustrate the use of the foregoing method, let it be 
required to estimate the flood-flow of a certain stream of a drainage-area of 
50 square miles, with steep side slopes and a long valley. The length of the 
valley is, say, 15 miles, and actual length of the main channel 25 miles, with 
5 miles of smaller channels reaching to the farthest part of the area. * The 
time required for the water to get to the small channels may be one hour, to 
flow the 5 miles two hours, and the 25 miles eight hours, or a total of 
eleven hours. The summer rainfall to be expected in this time is, from Fio-. 
12, p. 49, about 6 inches, or at the rate of about 13 inches in 24 hours. The 
percentage may be taken at 50, giving therefore a rate of flow of 6^ inches per 
24 hours, or 174 cubic feet per second per square mile. Or, using the diagram 
of Fig. 13, we find that for a time value of 11 hours and a percentage of 50 
the flood-flow is about 180 cubic feet per second per square mile. 

For a stream of the same area but having a watershed nearly circular, the 
distance would be reduced to perhaps one-half the above, and the time to six 
hours, corresponding to a rainfall of 5 inches or a rate of £ inch per hour. 





























































MA XIM UA 1 FLOW . 7 3 

which, with a percentage of 50, would give the high rate of 270 cubic feet 
per second per square mile. 

72. Some Great Floods. —On March 30 and 31, 1889, there occurred a 
great storm over a large part of Pennsylvania and New York which caused 
very high floods in many streams. The great Johnstown disaster was one of 
the results of this storm. It was caused by floods in the South Fork of the 
Connemaugh River, a stream with a drainage-area of 48.6 square miles and a 
length of 10 miles. An estimate made by an investigating committee of the 
American Society of Civil Engineers* placed the maximum rate of flow at 
about 215 cubic feet per second per square mile. The rainfall amounted to 
from 6 to 8 inches on May 30 and 31, it being estimated that for several 
hours rain fell at the rate of § inch per hour. The estimated rate of flow 
would be equal to one-half of this. 

This same storm caused a flood in the Chemung River at Elmira, N. Y., 
a stream with a watershed of 2055 square miles, which was estimated by 
Mr. Collingwood at 138,000 cubic feet per second or 67.1 cubic feet per 
second per square mile.f The rainfall varied from 6 to nearly 10 inches, 
averaging about 7, the larger portion falling in 12 hours or less. The extreme 
length of the watershed is about 50 miles; the slopes are moderate, and it 
would probably require at least 24 hours for the maximum flood-point to be 
reached. On this basis the maximum flow of 67.1 cubic feet per second per 
square mile, or 2.5 inches per 24 hours, would be 35 per cent of the average 
rate of rainfall for this length of time. 

On Feb. 6, 1896, great floods were caused in New Jersey by a rain of 
about 3.7 inches (most of which fell in 24 hours) and the simultaneous melt¬ 
ing of snow estimated equal in amount to about 0.6 inch of rain, making a 
total of 4. 3 inches. Of this, from 2. 5 to 3 inches was discharged as flood-flow, 
the remainder being absorbed by the ground. J The total run-off was therefore 
about two-thirds or 66 per cent. The percentage for the first half of the flow 
would be perhaps 50. The effect of the snow was at first to retard the flow, 
but later to greatly increase it, thus virtually concentrating a large part of the 
precipitation into a few hours. The Raritan River, with a catchment area of 
879 square miles, reached its maximum flow in about 16 hours, the rate 
being 68 cubic feet per second per square mile. If 3 inches represent the 
precipitation during this time, the flow would then be estimated, according to 
the method of Art. 69, at 3 X . 50 = 1.5 inches in 16 hours, or 2.25 inches 
in 24 hours, equal to 61 cubic feet per second per square mile. The Passaic 
with a drainage-area of 822 square miles reached its maximum in 44 hours, 
and yielded only 22 cubic feet per second per square mile, the slowness of 
the rise and low maximum rate being due to extensive flats along the river. 
Estimating this in a similar manner, the rainfall would be the total amount, 
or 4.3 inches, and the flow equal to 4.3 X .50 X X 27 = 31.6 cubic feet 
per second per square mile. These two examples serve to show that, while 
all estimates of flood-flows will be only roughly approximate, yet the method 
given will lead to more rational results than the application of any formula. 

Data of the rise and flow of other New Jersey streams during this flood 
are given on the next page. They well illustrate the importance of taking 
account of features of a watershed other than mere extent of area. 

* Trans. Am. Soc. C. E., 1891, xxiv. p. 431. 

f Report New York State Engineer, 1894, p. 387. 

\ See Report Geological Survey of New Jersey, 1896. 




74 


FLO W OF STREAMS. 


The decrease in flow with increase in the time required to reach a maxi¬ 
mum is quite regular, with the exception of the Pequest, a stream having very 
large surface storage. 


Stream 

Approximate 
No. of Hours 
from Beginning 
to Maximum 
Flow. 

Discharge, 
Cubic Feet per 
Second per 
Square Mile. 

Drainage-area, 
Square Miles. 

Pequannock. 

7 

115 

48 

South Branch. 

8 

H 3 

67 

Whippany. 

10 

84 

38 

Wanaque. 

n 

99 

73 

Pequest. 

15 

13 

158 

Raritan.•. 

16 

68 

879 

Pompton. 

16 

65 

285 

Rockaway. 

16 

43 

118 

Ramapo. 

24 

54 

160 

Passaic.- . 

44 

22 

879 


The flood on the Sudbury River caused by the great rain-storm in New 
England in February, 1886, is described by Mr. FitzGerald in a paper before 
the American Society of Civil Engineers.* The total rainfall, including snow 
equivalent to 2 inches of rain, from 7 p.m., Feb. 10, to midnight, Feb. 13, 
was estimated at 6.64 inches, of which about 5.08 inches flowed off, or about 
75 per cent. The maximum rain in 24 hours was about 3 inches, and the 
maximum rate of flow was 1.54 inches per 24 hours, or about one-half that 
of the rainfall. The size of the drainage-area is about 78 square miles, and 
the topography an average for New England watersheds. On a neighboring 
stream of only 6.4 square miles of watershed the maximum rate of flow was 
1.801 inches per 24 hours. The two rates were thus nearly the same, as the 
heavy rainfall was of sufficient duration to affect fully the larger watershed. 

TOTAL FLOW FOR VARIOUS PERIODS OF TIME. 

73. Statistics of Stream-flow.—Valuable records of run-off are avail¬ 
able for a number of streams in the Eastern States that have been used 
or considered as a source of supply, but aside from these the informa-. 
tion is meager. The most valuable of the available data are sum¬ 
marized in Table No. 16, in which are given the average yearly, the 
minimum yearly, and the seasonal flows, with corresponding rainfalls. 

The characteristics of the various watersheds are briefly as follows: 
The Sudbury, Cochituate, and Mystic have been for many years the 
sources of Boston’s water-supply. The Sudbury watershed is hilly 
and has steep slopes, but contains some large swamps; the Cochituate 
watershed is flat and sandy, while the Mystic is of an intermediate 
character. All have a very considerable percentage of forest area. 
The Connecticut River has a rugged watershed with about half the area 


* Trans. Am. Soc. C. E., 1891, xxv. p. 253. 
























STATISTICS OF THE FLOW OF STREAMS 









THE TOTAL RUN-OFF . 




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f In his report on New York’s Water-supply, 1900, Mr. Freeman concludes that the estimates of run-off for the Croton have been 
about 10 per cent too high. 
















































































76 


FLOW OF STREAMS. 


fallow or timbered. The Croton is a hilly watershed with about 30 
per cent timbered. The upper Hudson is a rugged mountainous 
'watershed with about 70 per cent in forest. The Genesee has moderate 
slopes and only 25 per cent of forest area. The Passaic has 58 per 
cent of forest area and is of varied topography, some parts being very 
hilly and others quite flat. The Perkiomen, Tohickon, and Neshaminy 
are small streams near Philadelphia. Their watersheds are hilly, with 
elevations from 250 to 1000 feet high, and contain areas of timber and 
waste land equal to 25 per cent in the case of the first two streams, 
and 7 per cent in the case of the Neshaminy. The Potomac watershed 
has steep mountainous slopes with a large proportion of forest and 
waste land. The Savannah lies mostly in a rolling country with a 
considerable percentage of forest area. The Des Plaines, a stream 
near Chicago, has a watershed of very flat slopes, a considerable 
amount of low swampy land, and very little forest area. The water¬ 
shed of the upper Mississippi is heavily wooded and nearly level. 
The percentage of water-surfaces on the various areas is, for the 
Sudbury about 3 per cent, the Cochituate 7.6 per cent, the Mystic 
3 per cent, the Croton 1.8 per cent, the upper Mississippi 18 per cent, 
and for the others less than 1 per cent. 

The very considerable variation in average percentage flowing from 
the different watersheds, due to differences in climate and physical 
features, is quite marked. 

74. Minimum Yearly Flow.—From the data given in the table it 
appears that the least yearly run-off for some of the streams of the 
upper Atlantic coast region is only 9 or 10 inches, or about one-half 
the average run-off. For the Genesee it is only 6.67 inches. The 
data for the Massachusetts streams cover a very great drought and are 
considered by those of experience as being safe for future estimates in 
that region. That such low values of run-off have not occurred on 
many of the other watersheds appears to be mainly due to the fact that • 
the rainfall has never been so low at those places during the period 
covered by the records. There seems to be no reason, however, why 
it may not at some future time be equally low. 

It is important to note that in dry years the proportion of the pre¬ 
cipitation flowing off is much smaller than the average, and, in general, 
the smaller the rainfall the smaller is likely to be the proportion running 
off. In California, for example, it is estimated by Le Conte * that in 
the vicinity of San Francisco, when the yearly rainfall is 10, 20, 30, 


* Trans. Am. Soc. C. E., 1892, xxvii. p. 292. 






THE TOTAL RUN-OFF. 77 

40, or 50 inches, the flow is approximately 0.5, 2, 9, 18, and 30 
inches, respectively. The percentages thus vary from 5 to 60. 

Like yearly rainfalls will not necessarily give like flows, as the 
amount flowing depends much upon the distribution of the rain 
throughout the year, and upon whether it is concentrated in a few large 
storms or is more evenly distributed. The least flow for a given yearly 
rain is caused by a combination of unfavorable conditions, and in 
making estimates such least flows are the ones to be considered. 
Fig. 14 represents by the shaded portion approximately the least flows 



for given rainfalls for most of the streams represented in Table No. 16, 
as determined from the detailed statistics. The dotted portions are 
extensions of the curves beyond the field covered by the data. The 
upper limit represents such streams as the Connecticut, Passaic, and 
Tohickon, and the lower curve the Cochituate, while the curves for 
most of the other streams fall somewhere between these limits. The 
upper Hudson falls somewhat above the diagram, and the Genesee 
below. The Des Plaines and upper Mississippi fall far below. In 
some cases the curve for a stream will be low at one end and high at 
the other, as, for example, the curve for the Mystic. For very low 
rainfalls this watershed gives as low a yield as the Cochituate, but 
for rainfalls of 40 or 50 inches the run-off is much greater. 

According to this diagram, the least run-off to be expected from 
ordinary watersheds in the Eastern States for a rainfall of, say, 40 inches 
would probably be somewhere between 12J- and 18 inches, depending 
upon the character of the watershed. For a rainfall of 30 inches the 
least flow to be expected would be between and 12J inches. 


































































78 


FLOW OF STREAMS. 


For other parts of the United States having about the same general 
distribution of rainfall, these data and curves will be of assistance in 
making approximate estimates. The effect of varying yearly rainfalls 
will at least be similar to that shown by the curves in the figure, and 
with this kept in mind even one or two years of gaugings will be of 
much value. For localities with a much different distribution of rainfall 
than in the Eastern States it will be necessary to consider carefully 
this distribution as shown below. 

75. Monthly and Seasonal Flow. —The average monthly flow, 
together with the average monthly rainfall, is shown for several streams 
in the diagram Fig. 15. There are also given in Table No. 16 the 


Fo/rtfa// 



/? un-off - 1 

Fig. 15.—Average Monthly Stream-flow. 


average rainfall, run-off, and percentage running off for the six moncns 
from June to November, and for the six months from December to 
May, the former period being in general the six months of least pro-, 
portionate flow, and the latter that of greatest flow. From these 
figures and diagrams the small value of summer rains in furnishing 
water to the streams is evident. 

A detailed analysis for the several years shows that what was true 
for yearly rainfall is also true for seasonal, namely, that the less the 
rainfall the less the percentage flowing off. The relation between rain¬ 
fall and run-off is represented approximately by the curves in Fig. 16, 
which is constructed similarly to Fig. 14, using here seasonal rainfall 
and seasonal flow. The diagrams represent by the shaded portions 
minimum values of run-off which may be expected for various seasonal 


l 



































































































THE TOTAL RUN-OFF. 79 

% 

rainfalls for the same streams as are represented in Fig. 14. They will 
be of some service in estimating stream-flow where the rainfall has a 
somewhat different distribution than upon the watersheds in question. 

Detailed statistics pertaining to the Sudbury River for the years 
from 1879 to 1884 are here appended in Table No. 17, p. 80.* They 
furnish a good illustration of the variation in stream-flow from month to 
month, and cover the most critical period so far observed in that region. 



They form the basis of storage computations mentioned in Chapter XV. 
The effect of the difference in the distribution of the rainfall in the 
years 1880 and 1882 should be noted. Compare also the data for 
1880 and 1883. 

76. Estimates of Flow.— The data in the preceding articles will 
enable fairly close estimates to be made of the amount of run-off for 
streams in the Eastern States or for regions of like characteristics. 
For other regions rough estimates may still be made by a judicious 
use of the data in connection with rainfall statistics, and by a careful 
consideration of the influences affecting evaporation and percolation. 

In any given case the years for which estimates are required are 
those of least flow; and since it is not usually desirable to have 
impounding-reservoirs for water-supply purposes drawn below the 
hirh-water line for more than two or three years at a time, the pei iod 
covering the two or three driest consecutive years is all that need be 
investigated. Rainfall data for such periods can be obtained from 
Chapter IV, and also the average distribution during the two parts of 
the year (Table No. 6, page 45). This being known, approximate 
estimates of the seasonal flows can then be made from the diagiams of 
Figs. 14 and 16, making allowance as far as possible for differing con¬ 
ditions. In making use of these diagrams it should be borne in mind 


* Mass. Board of Health Reports. 





























































8o 


FLO W OF STREAMS. 


that the minimum curves represent extreme conditions, such as would 
obtain for a single season or a single year only. In considering a 
number of consecutive years or seasons the values given by these 

TABLE NO. 17 . 


RAINFALL RECEIVED AND COLLECTED ON THE SUDBURY RIVER WATERSHED, 

1879-18S4. 


Months. 

1879. 

1880. 

1881. 

Sh 

c 

« 

Rainfall 

Collected. 

Per cent 
Collected. 

Rainfall. 

Rainfall 

Collected. 

Per cent 

Collected. 

Rainfall. 

Rainfall 

Collected. 

Per cent 

Collected. 

January. 

2.48 

I.25 

50.4 

3-57 

2.00 

56.02 

5 - 56 

O.74 

13-31 

February. 

3-56 

2.76 

77-4 

3-98 

2.98 

74.92 

4-65 

2.49 

53.62 

March. 

5 -i 4 

4.16 

80.9 

3.32 

2-45 

73-93 

5-73 

7.14 

124.64 

April. 

4.72 

5 o 8 

114.1 

3 - 11 

2.02 

64.97 

2.00 

2.67 

133-44 

May. 

1 .53 

I.99 

125.8 

1.84 

O.92 

49-95 

3 - 5 i 

I.72 

49-°3 

June. 

3-79 

O.71 

18.8 

2.14 

0.30 

14.16 

5-40 

2.30 

42.80 

July. 

3-93 

O. 28 

7 -i 

6.27 

0.32 

5-02 

2-35 

O.49 

20.98 

August. 

6. 51 

O. 71 

10.8 

4.01 

O. 21 

5-29 

1.36 

O. 26 

19-45 

September. 

1.88 

O.24 

12.9 

1.60 

0.14 

8.64 

2.62 

0-34 

13-01 

October. 

0.81 

O.13 

15-6 

3-74 

O. l8 

4-85 

2.96 

0-33 

11.20 

November. 

2.68 

0.36 

13.2 

1.79 

0-35 

19.85 

4.09 

0.68 

16.66 

December. 

4-34 

0.83 

19.0 

2.83 

0.31 

11.05 

3 - 9 6 

1.38 

34-93 

Total and averages. 

41.42 

18.76 

45-3 

38.18 

12. l8 

3 I- 9 I 

44.17 

20.57 

46.56 


1882. 

1883. 

■4* 

00 

00 

M 



xi 

•d 


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• 

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cu 

Pi 

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cu 

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5-95 

2.21 

37-19 

2.81 

0.60 

21.25 

5-09 

I . 78 

34-91 

February. 

4-55 

3-87 

85.18 

3-87 

1.66 

43 05 

6-55 

4-74 

72.45 

March. 

2.65 

5-06 

191.16 

1.78 

2.87 

161.42 

4.72 

6-75 

143.06 

April. 

1.82 

1.50 

82.09 

1.85 

2-33 

126.27 

4.41 

4-93 

111.82 

May.. • • 

5-07 

2.30 

45-48 

4.19 

1.67 

39 - 9 6 

3-47 

1 . 84 

52.97 

June. 

1 . 6b 

0.91 

54-87 

2.40 

0.52 

21.58 

3-45 

0. 72 

20.86 

July. 

1.77 

0.15 

8.70 

2.68 

0.21 

7.68 

3-67 

0.40 

10.89 

August. 

1.67 

0.10 

5 - 9 i 

0.74 

0.14 

19.06 

4.65 

0.46 

9-85 

September. 

8.74 

0-53 

6.05 

1.52 

0.16 

10.36 

0.86 

0.08 

8.8> 

October. 

2.07 

0-53 

25-74 

5-60 

0.33 

5.92 

2.48 

0.15 

5.98 

November. 

115 

0.36 

3 I- 5 I 

1 . 81 

o -35 

19.52 

2.65 

0.30 

11.44 

December. 

2.30 

0.56 

24-45 

3-55 

0-35 

9.72 

5 -i 7 

1.65 

3 i- 9 i 

Total and averages. 

39-39 

M 

OO 

M 

O 

45-95 

32.78 

11.19 

34-13 

47.14 

23.78 

50.46 









































































































THE TOTAL RUN-OFF. 


Si 

curves should therefore be used for but one or two such periods, much 
more liberal values being assumed for the remainder, or for the 
average. 

If the watershed contains large areas of water-surface, it is important 
that proper allowance be made for the evaporation from such surfaces, 
data for which are given in Chapter V. 

77. Effect of Lakes and Ponds on Stream-flow. —The result found by 
the preceding method takes no account of the effect of lakes and ponds 
acting as storage-reservoirs; the calculations would indeed often indicate 
a negative flow due to evaporation from excessive areas of water-sur¬ 
face, when in reality the flow is rendered more steady and continuous 
by such ponds, although the total yield may be much diminished 
thereby. This equalizing effect of natural ponds depends upon the 
amount their flow-line can be lowered, that is, upon the available 
storage contained therein; and can be more easily and logically taken 
account of in connection with the question of artificial storage. 
(Chapter XV.) 

78. Example of Estimate of Flow. —As an example, let it be required to 
estimate the yield per square mile of a watershed containing 10 per cent of 
water-surface, having moderate slopes, and about two-thirds in meadows and 
under cultivation, the remainder being forest area. Suppose the rainfall dis¬ 
tribution and evaporation to be as given for Davenport, Iowa, in Tables 
Nos. 6 and 11, pp. 45 and 56; but for safety we will take 0.55, 0.65, and 
o. 70 as the ratios to the average, of the rainfalls for the one, two, and three 
driest years respectively, the average rainfall being 33.3 inches. Assuming the 
distribution of the rainfall in dry years to be the same as the average, we will 
have the following rainfalls in each six months of the three consecutive years, 
putting for convenience the driest year second and the wettest year first: 

First Year. Second Year. Third Year. 

Total. 26.5 inches 18.3 inches 25.1 inches 

December-May. 11.1 “ 7-7 “ 10.5 “ 

June-November. 15.4 “ 10.6 “ 14.6 

By the aid of Fig. 16 we may then estimate the flow for each six-month 
period. On account of the flat slopes and agricultural character of the 
country, the area in question would not be classed higher than the poorest of 
those represented in the diagram. For the driest year we may therefore 
assume the flow according to the lowest curves, giving about 4 inches and 
o inch as the least flows to be expected for the two six-month periods of the 
second year. For the third year, with rainfalls of 10.5 and 14-6 inches for 
the two seasons, we would have run-offs of perhaps 5^ inches and 1 inch 
respectively; and for the first year, allowing somewhat more liberal figures, 
we may estimate the flow at 6^ and 2 inches. 

The run-off for the driest year is so small that it is largely dependent 
upon ground-storage and upon the occurrence of a part of the rainfall in 
heavy storms. That such small flows may be expected as are here given 





82 


FLOW OF STREAMS. 


can be seen by a reference to the data for the Des Plaines in Table No. 16. 
The flow of this stream, it may be noted, ceased altogether for a time in 
nearly every summer during the observations; and furthermore, of the 3.19 
inches flowing in the year 1895, 1.80 inches flowed in the month of Decem¬ 
ber, leaving but 1.39 inches for the previous eleven months. 

So far the estimates are for land-surface only, or for a watershed with in¬ 
significant water-areas. To these values must now be added or subtracted 
the excess or deficiency of rainfall over evaporation from the 10 per cent of 
water-surfaces, the evaporation data being taken from Table No. n, Chapter 
V. This gives a negative flow in some cases, which means that evaporation 
from the lakes and ponds exceeds the natural flow from the area. The various 
items are recapitulated in Table No. 18. 

To estimate the distribution of the stream-flow throughout the various 
months it is sufficiently close, and as accurate as the above method of estima¬ 
tion warrants, to assume the excess of winter’s flow over summer’s flow to be 
all concentrated in the four months, January to April, and as uniformly dis¬ 
tributed over these months. The remainder may be assumed as uniformly 
distributed over the entire year. As regards the necessary storage-volume, 
the exact distribution of the flow whenever it exceeds or falls short of the 
average consumption is of no consequence, the only matters of importance 
being the total amount of excess or deficiency and the time when such excess 
or deficiency begins. Where a negative flow occurs it is subtracted from the 
flow for the succeeding period, and the remainder assumed as flowing in the 
four months of January to April. The results are given in Table No. 18, in 
gallons per day for the two periods, January to April, and May to December. 

Instead of using general percentages for the rainfall for dry periods, and 
an average distribution of the rainfall, the actual rainfalls might have been 
used. In either case, however, the results must be looked upon as but a 
rough indication of what the flow is likely to be. 

TABLE NO. 18 . 


ESTIMATE OF FLOW FOR THREE DRY YEARS FROM ONE SQUARE MILE OF WATERSHED 

CONTAINING TEN PER CENT OF WATER-SURFACES. 




Flow from 
Land-surfaces. 

Flow from Water- 
suifaces. 


Net Flow. 

Period. 

Oj 

£ 

!3 

Total. 

9°% 

Evap- 

Rainfall Minus 
. Evaporation. 

C/5 

-C*5 

O 2 
ctf 0 

Gallons per Day. 


Inches. 

Inches. 

Inches. 

oration. 

Inches. 

Total. 

Inches. 

10 # 

Inches. 

v * 

<-></) 

c 

HH 

Jan.-Apr. 

May--Dec. 

First Year: 










Dec. to May... 

II. I 

6.5 

5.35 

II .6 

~ 0.5 

— O.05 

5.80 

800,000 


June to Nov.... 

15.4 

2.0 

i. So 

27.4 

— 12.0 

— 1.20 

O. 60 

60,000 

Second Year: 










Dec. to May... 

7-7 

4.0 

3.60 

ii. 6 

- 3-9 

- 0-39 

3-21 

460,000 


June to Nov.... 

10.6 

O 

0 

27.4 

— 16.8 

-1.68 

-1.68 

O 

Third Year: 










Dec. to May.... 

10.5 

5-5 

4-95 

11,6 

— 1.1 

— 0. II 

4.84 

450,000 


June to Nov.... 

14.6 

1.0 

0.90 

27.4 

— 12.8 

— 1.28 

-0.38 

O 




































LI TER A TURK. 


83 


LITERATURE. 

1. Herschel. The Gauging of Streams. Trans. Am. Soc. C. E,, 1878, 

vii. p. 236. 

2. Report of Committee on the Gauging of Streams. Proc. Am. Soc. C. E., 

1879, v - P- io 9 - Contains table on maximum and minimum flow. 

3. Fteley. Flow of Sudbury River, Massachusetts, for the years 1875 to 

1879. Contains data on maximum and minimum flow. Trans. 
Am. Soc. C. E., 1881, x. p. 225. 

4. Brackett. Rainfall Received and Collected on the Watersheds of Sudburv 

J 

River, and Cochituate and Mystic Lakes. Jour. Assn. Eng. Soc., 
1886, v. p. 395. 

5. FitzGerald. Yield of the Sudbury River Watershed in the Freshet of 

February 10-13, 1886. Trans. Am. Soc. C. E., 1891, xxv. p. 253. 

6. Report of the Committee on the Cause of the Failure of the South Fork 

Dam. Trans. Am. Soc. C. E., 1891, xxiv. p. 431. 

7. FitzGerald. Rainfall, Flow of Streams, and Storage. Trans. Am. Soc. 

C. E., 1892, xxvii. p. 304. 

8. Babb. Hydrography of the Potomac Basin. Trans. Am. Soc. C. E., 

1892, xxvii. p. 21. 

9. Babb. Rainfall and Flow of Streams. Trans. Am. Soc. C. E., 1893, 

xxviii. p. 323. 

10. Mead. The Hydrogeology of the Upper Mississippi Valley and of some of 

the Adjoining Territory. Jour. Assn. Eng. Soc., 1894, xm. p. 329. 

11. Vermeule. Report on Water-supply. Geolog. Survey of N. J., 1894, 111. 

Data relating to many streams are here brought together and discussed. 

12. Geolog. Survey of New Jersey, 1896, p. 257. The floods of Feb. 6, 1896. 

13. (a) Newell. Results of Stream Measurements. U. S. Geolog. Survey, 

1892-3, p. 89. 

( b ) Leverett. The Water Resources of Illinois. U. S. Geolog. Survey, 
1895-6, Part II, p. 701. 

Besides the above-named papers, the reports of the Survey since 
1888, the Bulletins, and the Water-supply and Irrigation Papers con¬ 
tain much valuable information relating to the hydrography of the 
United States. 

14. Report State Engineer, N. Y., 1894, p. 387. The flood in the Chemung 

River. The reports for 1895 and 1896 contain data relating to the 
upper Hudson and the Genesee. 

15. Johnston. Data Pertaining to Rainfall and Stream-flow. Jour. W. Soc. 

Eng., 1896, 1. p. 297. Relates chiefly to the Des Plaines River. 

16. Report Chief of Engineers, U. S. A., 1896, p. 1843. Data relating to 

the upper Mississippi. 

17. Wegmann. The Water-supply of the City of New York. N. Y., 1896. 

Data relating to the Croton. 

18. Annual Reports of the Water Bureau of Philadelphia. Contain complete 

data relating to the Perkiomen, Tohickon, and Neshaminy. 

19. Reports of the Boston Water Board and of the Metropolitan Water Board 

(Boston). Monthly data relating to the Sudbury, Cochituate, and 
Mystic. 

20. Chamier. Capacities Required for Culverts and Flood Openings. Proc. 

Inst. C. E., 1898, cxxxiv. p. 313. 


CHAPTER VII. 


GROUND-WATER. 

GENERAL CONSIDERATIONS. 

79. Occurrence of Ground-water. —I-n Chapter V it was shown that 
water precipitated upon the earth’s surface in any form is disposed of 
in three ways: by evaporation, by surface-flow, and by percolation. 
In Chapter VI the stream-flow was shown to include both the surface- 
water and the water of percolation. In the present chapter it is pro¬ 
posed to deal with the last-mentioned portion more in detail, as to its 
quantity, movement, and availability as a direct source of supply. 

Percolating water that escapes beyond the reach of vegetation must, 
in obedience to the law of gravitation, pass on downward until it 
reaches an impervious layer of some sort. The immediate impervious 
stratum is the surface of the water which has preceded it and which 
has in past ages filled every pore and crevice of the earth’s crust up to 
a certain level at which the escape of the water laterally becomes equal 
to the addition from percolation. The accumulation of water which 
thus exists in the ground is called ground-water, and its surface th^ 
ground-water level or the water-table. 

In limestone regions it is sometimes the case that quite large 
streams are found flowing underground, and large cavernous spaces 
may be converted into underground lakes of considerable size, as in 
the great caverns of Indiana and Kentucky. Such bodies of water 
are, however, rarely available for a water-supply, and it may be taken 
as a safe rule that for ground-water supplies dependence must be 
placed upon the water which percolates into and flows through the 
pore-spaces in soils and rocks, the amount of which is strictly 
dependent upon the rainfall and the laws of hydraulics that govern the 
flow. 


84 


GENERAL FORM OF THE WATER-TABLE. 


85 


80. General Form of the Water-table. —Under the action of gravity 
the surface of the ground-water always tends to become a level surface, 
and as long as a supply is maintained through percolation there will 
be a continual lateral flow which will on the average be equal to the 
percolation. In surface streams a very slight inclination is sufficient 
to cause a rapid movement of water, but in the ground the resistance 
to movement is so great that a relatively steep gradient is necessary to 
maintain even a very low velocity. 

If we imagine the ground to be throughout of uniform porosity, the 
ground-water surface will conform in general outline to the ground- 
surface, but with less variations. Such an ideal condition is repre¬ 
sented in Fig. 17. At the margin of streams the level of ground- and 



Fig. 17.—General Relation of Surface of Ground-water to the Surface 

of the Earth. 

surface-waters will coincide.* Passing back from the stream the 
ground-water level will gradually rise, but at a less rate than the 
ground-surface, then descend again into another depression, etc. In 
the valley there is also a fall parallel to the stream, corresponding to 
that of the surface-water, and the direction of flow will be towards and 
slightly down the stream in the line of greatest declivity. 

Increased percolation will raise the level of the ground-water, but 
less rapidly at the outlet than elsewhere, thus increasing the gradient 
and consequently the flow. During a period of drought the flow will 
continue at a slower and slower rate, due to decreased gradient, until 
the water ceases to flow laterally into the stream; the stream then 
becomes dry, and the flow continues at a slow rate parallel to the 
valley and entirely underground. Thus in a region where the forma¬ 
tions are very porous and where the slopes are very steep, large 
streams will disappear and flow for long distances underground. 

In any actual instance the ground is usually far from having the 
uniform porosity as assumed in the ideal example above; and the areas 
to be studied will ordinarily consist of alternating strata of coarse 
porous materials, and of fine and more or less impervious deposits. 




86 


GRO UND- WA TER. 


In general the change from coarse to fine material in the direction 
of flow will be accompanied by an increased gradient in the ground- 
water level owing to the increased resistance; and conversely. If the 
gradient necessary to carry the quantity of water reaching the section 
in question is greater than the surface gradient, an overflow to the sur¬ 
face takes place, thus giving rise to a marsh or to a surface stream. 
Overflows thus occur frequently at the foot of hills where the ground- 
water surface is apt to be at a very small depth. 

Variations in ground-water level take place comparatively slowly, 
following gradually the variations in yearly, seasonal, and briefer 
periods of rainfall. Near streams and in lowlands the level varies 
little, being fixed largely by the level of the adjacent surface-water. 
At higher points in the water-table the level is subject to correspond¬ 
ingly great fluctuations, often many feet in extent. In porous material 
where slopes are small the variations are small. 

81. Porosity of Soils. —All soils and rocks near the surface of the 
€arth are capable of absorbing more or less water. 

If the particles of a body of sand or soil were of uniform size and 
perfect spheres, and arranged in the most compact manner, the volume 
of pore-space would be about 26 per cent of the total volume. Owing 
to irregularities in form and arrangement the porous space is usually 
greater than this. In sand of a fairly uniform size it is commonly from 
35 to 40 per cent. Mixed sand and gravel will have a smaller per¬ 
centage of voids, the decrease depending on the variation in size of 
particles; but it will seldom be less than 25 per cent. Rocks will vary 
in porosity from a very small fraction of 1 per cent in the case of some 
granites to 25 or even 30 per cent for some loose-textured sandstones. 

The amount of moisture which a soil or rock will absorb is, how¬ 
ever, not of so much importance to the water-works engineer as is the 
carrying capacity and the amount which can readily be drawn frorp 
such material when previously saturated. In fine soils the movement 
of the water is so slow and such a large part of the water is retained 
by capillary action that such soils are of little value as carriers of 
water; and to obtain economically the large quantities required for 
public supplies it is necessary that the water-bearing material be of a 
very open, porous character. Adequate supplies are rarely obtained 
from anything but sand and gravel deposits, or from very porous rock. 

The absorptive capacities of various rock formations and of soils are 
given in Table No. 19. 

82. Formations Favorable for the Transmission of Ground-water_ 

Rock formations are divided into two general classes, the igneous and 


FORMATIONS FAVORING TRANSMISSION OF GROUND-WATER . 87 

* 

TABLE NO. 19 . 


POROSITY OF VARIOUS FORMATIONS, IN PER CENT, BY VOLUME. 


Formation. 

Locality. 

Porosity 

Percentage.* 

Authority. 

Gra n i te . 


0.02 to 1.5 


Tlnlnmitp . 

Joliet, Ill. 

Red ford . Tnd. 

2.7 

9.8 

Merrillf 

4 4 

T imp^tnnp foblitirl .. 

F) ol r>m i te. 

W i n 0 n a , Minn. 

II. 7 

4 4 

Sla nH stone . 

Marquette, Mich. 

Fort Snelling, Minn. 
Jordan, Minn. 

Medina, N. Y. 

10.8 

4 4 

4 4 

13-9 

23-7 

4.4 

13.2 

12 to 26 

44 

4 i 

4 4 

l i 

4 4 

4 4 

Rerea O. 

4 4 

Ra trot a sandstone . 

Colorado 

Gilbert^ 

Buckley§ 

4 4 

4 4 

(~rra nite . 

Wisconsin 

0.019 to 0.62 

13-17 

11.66 

Lower magnesian limestone.. 

T imestone. . . 

Bridgeport, Wis. 
Fountain City, Wis. 
Duck Creek, Wis. 
Sturgeon Bay, Wis. 
Dunnville, Wis. 

Trenton limestone . 

1.04 

0.58 

28.26 

4 4 

Mia era ra 1 i m P<stBTlP. - - ... . . . . . 

4 4 

Pntsrlam <;flnH<stnnp . 

4 4 

u a 

Lake Superior, Wis. 
Ablemans, Wis. 
Argyle, Wis. 

England 

4 4 

20.19 

7.12 

19.06 

14 to 17 

14 to 44 

35 to 45 

25 to 30 

41.8 

37 to 45 

44 

4 4 «« 

44 

Peter sandstone. 

44 

T imestone ( odl iticL.......... 

Humber|| 

4 4 

Chalk . 




Qo nd and or r Q Vf* 1 _ _ .. 



Sandv soil... ................. 

South Carolina 

WhitneyU 

4 4 

Trimly land .... 

Maryland 




* The figures from Merrill were obtained by multiplying his “ ratio of absorp- 
tion ” by the specific gravity of the stone. 

f Stones for Building and Decoration. New York, 1897. 

\ Report U. S. Geolog. Survey, 1895-96. p. 584* 

§ Bulletin No. 4, Wisconsin Survey, 1898. 

|| Water-supply of Cities and Towns, p. 47* 

1 Bulletin No. 4, Weather Bureau, 1892, p. 25. 

the sedimentary rocks. To the former class belong the granites, 
syenites, and gneisses; these rocks are usually very dense and 
impervious and therefore poor water-carriers, but occasionally they 
jYjg^y furnish considerable water by virtue of theii decomposed and 
fissured condition near the surface. Of the sedimentary rocks, those 
composed of very fine-grained material, such as the clays, shales, and 
other argillaceous deposits, are relatively impervious. Limestones and 
dolomites contain little water as a lule, but if fissured the\ ma\ be the 
source of considerable supplies. The most favorable formations, by 
far, for furnishing large quantities of water, are the various sandstones, 
conglomerates, and gravel deposits. Sandstones are found which \aiy 
in texture from a very compact rock having a very small degree of 










































GRO UND- WA TER. 


88 


4g 

porosity to a material almost as porous as sand. Uncemented sands 
and gravels are of course the most favorable as regards porosity, but 
they are apt to be rather limited in extent. 

83. Occurrence of Water-bearing Formations. — In studying the 
various water-bearing formations from the engineer’s standpoint, it will 
be convenient to divide them roughly into three classes, depending 
upon their extent and outline. 

(1) Broad extensive formations of porons material, usually of con¬ 
siderable thickness and of a fairly uniform character over large areas. 
In the case of formations of this class comparatively few widely 
scattered borings will often serve to give a reliable knowledge of the 
strata, and wells may be sunk many miles apart with confidence as to 
the result. Most of the deep and artesian water of the United States 
is obtained from such formations, some of which underlie great areas of 
country. In England an example of such a formation is the immense 
deposit of chalk which underlies a large part of the country and 
furnishes much water for public supplies. The Tertiary deposit of sand 
and gravel underlying the marl throughout a large portion of the 
Western plains is supposed to have once been the bed of an inland sea. 
The so-called underflow, or ground-water of the plains, lies chiefly in 
this formation, and wells sunk to this stratum at any point are unfailing. 
These deposits are estimated at from 17 to 120 feet thick. Other 
examples of extensive water-bearing formations are given in Arts. 


101-103. 

(2) Deposits of porous material in old lake and river-beds often 
furnish very good collecting-areas for ground-water, and many of the 



shallower ground-water supplies are from such sources. These deposits 
are usually covered by other and less pervious strata, and indeed often 
consist of a series of strata alternately of a pervious and nonpervious 
nature. This is particularly true of the lacustrine deposits in the basins 
of the Western mountain region. Fig. 18 is an ideal section through 
such a basin in California and shows many alternate layers of clay and 
gravel.* 


* Report on Irrigation, Part I. p. 321. (U. S. Pub. Document.) 














FLOW OF GROUND-WATER . 


89 


Old river-channels filled with debris of a porous character give rise 
bo veritable ground-water streams. These may be located some dis¬ 
tance from the modern streams, or may at places coincide with or 
underlie them, forming porous, gravelly beds. 

Examples of such ground-water streams are very numerous. 
Leipsic, Germany, is supplied from such a stream about 2 miles in 
width, 40 feet thick, and having a fall of about 6 feet per mile. The 
covering stratum is 6 feet thick, and the velocity of flow is estimated 
at about 8 feet per day.* Pueblo, Colorado, is supplied with water 
from a gravel-bed 66,000 square feet in cross-section with an average 
depth of 14 feet and a length of 25 miles. This deposit fills the former 
bed of a stream which now flows partly through and partly over the 
surface of the gravel.t Many of the Western streams where they 
emerge from the mountains are of a similar character. 

(3) Deposits of sand and gravel in the drift are often of consider¬ 
able extent, and furnish many ground-water supplies, but such deposits 
are apt to be very irregular in character and uncertain in extent. 
They occur as accumulations in former stream-beds and also in the 
form of thin, irregular strata, sometimes of considerable extent, lying 
for the most part in valleys and covered with more or less clay. 

Still another formation of much value in certain localities is the 
dune-sand, such as occurs so extensively in Holland and from which 
many of the water-supplies of that country are drawn. 

In seeking ground-water supplies a study of the geology of the 
region is essential to intelligent action. Such a study will generally 
enable a decision to be made as to whether or not a supply is likely to 
be obtained from the deeper strata, and will give much information as 
to the nature of the glacial or other surface deposits. The location of 
extensive deposits in valleys is often shown by wells in the vicinity, 
but at other times they can be located only by a careful study of surface, 
indications and by borings. 

FLOW OF GROUND-WATER. 

84. Methods of Determining the Flow of Ground-water.—When a 
particular ground-water source is to be investigated for a water-supply, 
the same question must be answered as in the case of a surface supply, 
namely, what is the quantity of water available from day to day from 
the given source ? In the case of a surface stream the rate of discharge 


* Jour. f. Gasbel. u. Wasservers., 1881, p. 686. 
f Eng. News, 1891, xxv. p. 53 - 




9 o 


GRO UND- WA TER. 


Is determined by multiplying the observed velocity by the cross-section 
of the stream, and such observations carried on for a considerable 
length of time will give the necessary information, In the case of a 
ground-water supply similar determinations would be desirable, but they 
are much more difficult to make. 

The best method of estimating capacity is by means of actual 
pumping tests carried on for a sufficient length of time to bring about 
an approximate state of equilibrium between the supply and the 
demand as determined by the level of the ground-water. It will rarely 
be practicable to continue such tests until perfect equilibrium is reached, 
for in many cases several years of operation would be required to deter¬ 
mine the ultimate capacity of a source. Pumping tests of short dura¬ 
tion are apt to be very deceptive, as the ground-water may exist in the 
form of a large basin or reservoir with very little movement, corre¬ 
sponding to a surface pond with small watershed, and brief tests would 
give but little more information than similar tests on a pond. 

Where it can be done it is very desirable to get an approximate 
idea of the amount of water actually flowing per unit of time through 
the area in question. This may be done by estimating the velocity of 
flow, the cross-section of the porous stratum, and the percentage of 
porous space; or an approximate estimate can sometimes be made by 
estimating the probable percolation on the tributary area. 

85. Formula for Estimating Velocity of Flow.—The velocity of flow 
of a ground-water stream is a function of the hydraulic gradient, or 
slope, on the one hand, and the resistance to flow offered by the 
particles of soil on the other. 

The slope can readily be determined by borings sunk to ground- 
water level, care being taken to measure it in the direction of greatest 
declivity. In case the porous stratum is overlaid by a more or less 
impervious one the water in the lower stratum may flow under a pres¬ 
sure greater than atmospheric. The slope or hydraulic gradient is then 
found by determining the height to which the water will rise in tubes 
sunk to the porous stratum, care being taken to prevent the escape of 
water between the tube and the upper strata. Samples of the material 
can also be obtained at the same time and examined as to size and 
porosity. The latter element is influenced not only by the variation in 
size of grain, but also by the degree of compactness of the material in 
its natural bed; it can therefore be only approximately determined from 
loose samples. The size can readily be determined by means of 
sieves.* 


* For further details relating to sand analysis, see Art. 511. 





FORMULA FOR ESTIMATING VELOCITY OF FLO W. 


9 I 


These elements having been determined, it remains to express the 
relation between them and the velocity of flow. 

Experiments by Darcy, Hagen, Hazen, and others show that the rate 
at which water at a given temperature will flow through any particular 
sand or fine gravel follows closely the law of flow through capillary 


tubes, that is, the velocity is approximately proportional to —, where 

L 


li is the head, and / is the distance through which the water flows. 
(In the case of a stream flowing through such material down a uniform 

, h 

slope, y would be the sine of the slope angle.) The velocity is 


also dependent upon the size of the grains of the material, it being 
nearly proportional to the squares of their diameters. 

The complete formula derived by Hazen * as applicable to sands of 
from o. 1 to 3.0 mm. effective size t is 


v = cd 2 


h [t (Fah.) + io c 


/\ 


6o° 



where v = velocity in meters daily of a solid column of the same cross- 

section as that of the sand ; 
c = a constant = approximately 1000; 
d = effective size of sand grains in millimeters; 
h = head of water causing motion; 

thickness of sand layer = slope of ground-water surface^ ; 


l 

t = temperature in degrees Fahrenheit. 


The sand experimented upon was fairly uniform, and, taking the 
porous space at 40 per cent, the average velocity of the water through 
the pores would be 2.5 times the above velocity. Neglecting the tem¬ 
perature corrections, as being in any case small for ground-waters, and 
expressing the velocity in feet, we have, as applicable to sands and 
gravels with d varying from o. 1 to 3 mm., 


v — "620od 2 s — ks, 



* Report Mass. Board of Health, 1892, p. 553. Slichter has from theoretical con¬ 
siderations derived a formula which takes account of the varying porosities of the 
material due to different degrees of compactness. Nineteenth Annual Report U. S. 
Geolog. Survey, p. 322. 

f Ten per cent of the sand finer than these dimensions. 





9 2 


GKO UND- WA TER. 


where v — actual average velocity through the pores of the sand in 

feet per day; 

d = effective size of sand; 

s = slope of free ground-water surface, or the hydraulic gradient; 

k — 8200 d 2 = velocity for a slope of unity. 

A sand of an effective size of o. 10 mm. would be called a very fine 
sand, one of 0.3 a medium sand, and one of 0.5 a very coarse sand, 
although much depends on the uniformity. 

In Table No. 20 are given values of k for various values of d. 
The size of the material and slope being known, the velocity of flow is 
found by multiplying the corresponding value of k by the slope. Thus 
the velocity of flow in a material of a fineness of .4 mm.—a coarse 
sand—and with a slope of ground-water of .001 will be approximately 
1312 X -OOi = 1.3 feet per day; in a fine gravel of 3 mm. size it 
would be about 74 feet per day. 

4 . || 

TABLE NO. 20 . 


VALUES OF k , OR OF V FOR S = I, FOR VARIOUS VALUES OF d IN EQUATION (2). 


d 

Millimeters. 

0.10 

0.20 

0.30 

0.40 

0.50 

0.80 

1.00 

2.00 

3.00 

k 

Feet per day. 

82 

328 

73 S 

1.312 

2,050 

5,248 

8,200 

32,800 

0 

0 

00 

to 


For sands of little uniformity, and mixtures of sand and gravel, the 
velocity will still depend on the size of the finer particles; and if the 
larger stones are neglected in the estimation of the effective size, the 
above formula may still be used as an approximation. 

Lembke suggests values of k as follows, based on experiments of 
Darcy, Krober, and others:* 


Material. k in Feet per Day. 

Sand and gravel. 9,400 

Coarse sand. 2,Soo 

Medium sand. 760 

Fine sand. 150 

86. Coefficient for Coarse Gravels .—For gravels larger than 3 mm. 
and containing little or no fine material, experiments indicate that the 
velocity increases at a less rate than the square of the diameter, and 




* Revue Univ. des Mines, 1888, 1. p. 155. 


































THIEM'S METHOD OF DETERMINING VELOCITY. 93 

I 

also less rapidly than the slope. Results of such experiments on 
screened gravel are given in Table No. 21 as indicating in a general 
way the variation in velocity in coarse gravel deposits. 

TABLE NO. 21 . 

VELOCITIES OF FLOW OF WATER IN FEET PER DAY IN SCREENED GRAVEL, ASSUMING 
40 PER CENT POROSITY. BASED ON EXPERIMENTS OF THE MASSACHUSETTS 

STATE BOARD OF HEALTH.* 


Effective Size in Millimeters. 


Slope, s. 

3 

5 

8 

IO 

T 5 

20 

25 

30 

35 

40 

.0005 

28 

82 

164 

246 

410 

656 

902 

1,230 

1,640 

2,050 

.OOI 

57 

172 

335 

475 

820 

1,210 

1,680 

2,250 

3.030 

3,690 

.002 

115 

328 

639 

902 

1,550 

2,250 

3,030 

3,930 

4,830 

5,820 

.OO4 

221 

631 

1,230 

1,700 

2,870 

3-930 

5,000 

6,060 

7.130 

8,200 

.006 

336 

918 

1,690 

2,250 

3,690 

5,080 

6,390 

7,620 

8,930 

10,100 

.008 

443 

1,160 

2,060 

2,780 

4,340 

5,900 

7,33o 

8,930 

10,400 

11.800 

.OIO 

549 

1,410 

2,460 

3.150 

5,000 

6,800 

8,440 

10,000 

11,500 



* Report, 1892, p. 555. 


87. Thiem’s Method of Determining Velocity.*—A method of deter¬ 
mining the velocity of ground-water which has been used with satisfac¬ 
tory results by Thiem is as follows: Three or four borings are sunk to 
ground-water in a line in the direction of flow. A large dose of salt 
is then put into the upper hole, and at frequent intervals analyses are 
made of water drawn from each hole below until the salt content has 
reached its maximum in each case, and the rate of movement is inferred 
from these results. 

At Stralsund, velocities of 12.9, 12.6, and 12.0 feet per day were 
found in this way, with a slope of 2 per cent; and a velocity of 13.1 
feet at another place. The former values would correspond to a value 
of k equal to about 625, or to that for a medium sand. 

88. Quantity Flowing.— The velocity of flow having been deter¬ 
mined, also the porosity of the material and the cross-section of the 

x porous stratum at right angles to the direction of flow, the total rate of 
flow will be the product of these three factors, or 

Q — velocity X area of cross-section x porosity = vAp — ksAp , (3) 

in which the units are the foot and day. Irregularities in cross-section, 
slope, and material will of course render the result more or less uncer- 


* Jour. f. Gasbel. u. JVasservers. , 1888, p. 18. 
































94 


GRO UND- WA TER . 


tain, but estimates made in this way will nevertheless be of very con¬ 
siderable value in examinations of ground-water sources. 

In Table No. 22 are given the rates of flow per square foot of cross- 
section for sands of different degrees of fineness and porosity, and for 
a slope of 1 per cent. For other slopes multiply by the slope expressed 
in per cent. 

TABLE NO. 22 . 


RATES OF FLOW OF GROUND-WATER FOR A ONE PER CENT SLOPE (s = .Ol) IN 
GALLONS PER DAY PER SQUARE FOOT OF CROSS-SECTION. 


Porosity, 

Per cent. 



Effective Size of Sand in Millimeters. 



.10 

• 20 

• 30 

.40 

• 5 ° 

.80 

1.00 

2.00 

3.00 

20 

1.2 

4.9 

II .0 

20 

3 i 

79 

123 

490 

1,100 

25 

i -5 

6.1 

13.8 

25 

38 

98 

153 

610 

1,380 

30 

1 .8 

7-3 

16.6 

29 

46 

118 

184 

730 

i, 66 o 

35 

2.1 

8-5 

19-3 

34 

53 

137 

215 

850 

1,930 

40 

2.4 

9.8 

22.1 

39 

61 

157 

246 

980 

2,210 


An inspection of this table will show clearly that it requires very 
extensive areas and collecting-works to obtain much ground-water from 
fine material; and even with coarse material, if the slopes are flat (they 
are frequently only one-tenth of 1 per cent), a relatively large cross- 
section must be available. 

89. Quantity Available.—The proportion of the ground-water that 
can be intercepted depends upon the character of the collecting-works, 
a question which will be discussed in Chapter XIV. The useful capacity 
of such a supply—the quantity which it can deliver daily throughout 
the year—depends upon the minimum rather than the average flow, 
and in determining the flow a dry period should be selected if possible. 
The natural storage furnished by the ground not only renders the flow 
ordinarily quite uniform, but enables the draught to more or less exceed 
the minimum flow; and if the nature of the works are such that the 
ground-water level can be considerably lowered, this natural storage 
can be made to increase very materially the daily capacity of the 
source. In estimating the capacity of a source by estimating the per¬ 
colation, this element of ground-storage must be taken into considera¬ 
tion. 

SPRINGS. 

90. Formation of Springs.—Springs are formed where, for any 
reason, the ground-water is caused to overflow upon the surface. The 


























FORMATION OF SPRINGS. 


95 


conditions causing their formation are varied and should be carefully 
studied in connection with the design of collecting-works, as upon 
them depend largely such questions as the constancy of flow, the 
possibility of increasing the yield by suitable works, and the probable 
success of a search for additional springs. According to differences in 
these conditions springs may be divided into three general classes, each 
of which will be discussed separately. 

91. First Class. —The most important class of springs is that in 
which the water, in its lateral movement, is brought to the surface at 
the outcrop of a porous stratum where it is underlain by a relatively 
impervious one (Fig. 19). The porous stratum may be sand or gravel. 



Fig. 19. 

or a porous rock; while the impervious layer is usually clay, or rock 
of an argillaceous character. 

If the porous material is fairly uniform, the springs will be scattered 
all along the outcrop and will be small in size, the larger amounts of 
water appearing in the valleys or re-entrant angles of the outcrop. If 
the porous deposit be much fissured, especially if the rock itself be 
fine-textured, the location of a spring is largely a matter of chance, 
although topography controls in a general way. 

There are many cases of large springs of this class, the supplies for 
some of the largest cities of Europe being obtained from such sources. 
The city of Vienna is supplied from springs 60 miles distant that occur 
at the outcrop of a fractured dolomitic limestone underlain by slate. 
The largest spring, the Kaiserbrunnen, has an average flow of about 
150 gallons per second, varying from 60 to about 250.* Munich 
receives its supply from galleries constructed in fissured slate, which 
collect the ground-water that previously appeared in part as springs at 
the surface of the slate, and in part flowed through fissures into the 
river below. Baden-Baden intercepts, by means of a gallery about 
2 miles long, several springs occurring at the junction of granite and 
overlying sandstone. The flow varies from 4 to 18 gallons per second, 
averaging about 8.t 


* Lueger, p. 410. 


\ Ibid., pp. 275, 400. 




9 6 


GRO UND- WA TER . 


In the United States many supplies of considerable amount are 
obtained from similar springs, the most noteworthy instance being 
perhaps that of Roanoke, Va. The supply there is from a spring 
issuing from the limestone and having a flow of about 5,000,000 
gallons per day. 

92. Second Class .—Under this class are considered those springs 
where the water-bearing stratum is covered to a greater or less extent 
by an impervious one, and which are therefore more or less artesian in 
character. In this case the water finds its way to the surface where 
the overlying impervious material is wanting, or through a fault, or it 
breaks through at places where it is not sufficiently strong or compact 
to resist the upward pressure. Most of the springs which occur in the 
drift are of this character, the alternating layers of sand and clay so 
often found there being favorable to their formation. 

In Fig. 20 is given a section showing the formations immediately 



Fig. 20.—String at Avon, Mass. 


surrounding a spring of this kind, located at Avon, Mass.* Here the 
water is carried by coarse gravel which is overlain by hardpan. The 
location of the spring at this point was doubtless due to some local 
weakness. The outcrop of the porous stratum lies considerably higher 
than the spring. 

In some cases springs of this character are fed by water coming 
long distances through extensive formations which at other points offer 
conditions favorable for artesian wells. Of such character are the 
artesian springs at the eastern outcrop of the Dakota sandstone 
(Art. 102). Conditions of this sort also give rise to the peculiar 
phenomenon of large fresh-water springs- which boil up in the ocean 
several miles out from the Florida coast, and it is supposed that the 
great springs in northern Florida are from a similar cause. 

93. The Third Class of Springs includes those in which the porous 


* Jour. R r ew Eng. IV. IV. Assn., 1896, xi. p. 160. 











YIELD OF SPRINGS. 


97 


stratum in the vicinity of the spring is neither overlain nor immediately 
underlain by an impervious one. They are mere overflows of the 
ground-water, and occur whenever the carrying capacity of the porous 
material is insufficient to convey the entire tributary flow. 

In a region where the soil is very porous to a considerable depth, 
the surface-flow of streams will commence only at a considerable dis¬ 
tance from the head of the valley, the point of beginning being a spring 
of larger or smaller size of the class under discussion. If the formation 
is quite uniform, the springs will be small and numerous, and the source 
of the stream will move up and down the valley according to the 
weather, the point of beginning being determined by the carrying 
capacity of the ground. If the formation is irregular, the springs tend 
to be larger in size. In irregular formations it also often happens that 
after having flowed on the surface for some distance the water will 
again disappear, only to reappear farther down the valley. Such 
action is noticeable in almost any small brook, but in certain parts of 
the country it occurs on a very large scale. Where springs are thus 
formed by water that has recently flowed on the surface the character 
of the water is likely to differ greatly from ground-water proper. 

94. Yield of Springs.—The yield of any particular spring can readily 
be determined by weir measurements, and if these are carried out 
through a period of drought they will give all needed information re¬ 
garding the supplying capacity of the existing spring. If, however, 
but a short series of gaugings is available, it will be necessary to make 
allowances for variations in rainfall; and a knowledge regarding the 
area of percolation, quality of soil, and possibilities in the way of 
ground-storage will be of assistance in ‘drawing conclusions. The 
possibility of increasing the flow should also receive attention. 

Springs of the first class will vary in yield with the variations in 
ground-water level, but will not wholly cease to flow if the water is 
intercepted by suitable constructions. The yield of a series of springs 
of this class would, if the lower stratum be impervious, be equal to the 
entire percolation on the tributary area. This area is determined by 
the direction of the slope of the ground-water surface, and does not 
always correspond with the watershed for surface-water. Thus in Fig. 
19 more water will appear at A than at B. 

Springs of the second class are apt to be much less affected by 
variations in rainfall than either the first or the third class. Their yield 
varies with the variation of the ground-water level in the area of perco¬ 
lation, and if this is many miles distant, as is the case with many artesian 
wells or springs, the flow may be practically invariable. In most 


9 8 


GRO UND- WA TER. 


cases, however, the deposits are local in extent and the variation is 
considerable. 

Where a spring of this class exists, investigation may show that the 
ground-water stream from which it is fed is of considerable size and 
that the water of the spring is but a small portion of the entire flow. 
In such a case the yield may be increased by simply enlarging the 
opening, or by sinking wells and pumping therefrom, as in the case of 
an ordinary ground-water supply. 

Springs of the third class are liable to very great fluctuations, the 
flow often ceasing entirely. Occasionally, owing to the concentration 
of large volumes of ground-water into a small area, conditions are 
favorable for large and steady yields. Springs of this class form the 
source of the Vanne, from which Paris draws a portion of its supply. 
The largest of these, “ Le Bime de Cerilly, ” has an average yield of 
about 50 gallons per second, with a minimum of 18 gallons. 

ARTESIAN WATER. 

95. General Conditions.—Whenever a water-bearing stratum dips 
below a relatively impervious one the former becomes in a sense a 
closed conduit, and if the flow out of this conduit at the lower end be 
impeded from any cause, the water will accumulate and exert more or 
less pressure against the impervious cover. The amount of this 
pressure will depend on the extent to which the flow is obstructed and 
on the elevation of the upper end of the conduit, that is, of the outcrop 
of the porous stratum. If a well be sunk through this impervious 



Fig. 21. 


stratum at any point, the water will rise in it in accordance with the 
pressure; and if the surface topography and pressure are favorable, the 
water may rise to the surface, or considerably above, in which case the 
well becomes a true artesian, or flowing, well. 

The obstruction to flow at the lower end of the porous stratum may 
be due to various causes, chief among which are the three following: 

i* The stratum may be turned up at the lower end, thus forming 
a synclinal, or a curved conduit, as in Fig. 21. In this case water 
entering at A could escape at the lower lip B, but at intermediate 



ARTESIAN WATER. 


99 


points would exert a pressure on the covering. If the resistance to 
flow were uniform, and no water could escape except at B, the decrease 
of head from A to B would be uniform, or in other words the hydraulic 
grade-line would be a straight line AB. Water would rise to this line 
in a tube sunk to the porous stratum, and a flowing well would be 
possible wherever the surface lies below this line. 

2. The inclined stratum may be subjected at its lower outcrop to 
hydrostatic pressure from the waters of the ocean, as actually occurs 
along a large part of the Atlantic and Gulf coasts of the United States. 
The conditions obtaining in that region are roughly shown in Fig. 22. 





Fig. 22.—Artesian Conditions near Ocean. 


In this case a porous stratum outcropping at A and passing into the 
ocean at B would be subjected to a pressure throughout its length, vary¬ 
ing according to some hydraulic grade-line A C. Flowing wells are 
here possible at all points where the surface falls below this line. 

3. An increased resistance to flow is frequently caused near B } Fig. 
22, by increased density of the stratum or by a decrease in thickness. 

Such increased resistance will have the effect to increase the slope of 

« 

the hydraulic grade-line at the point of greater resistance, and give it 
a form something like the line ADC , thus making conditions still more 
favorable for flowing wells. Complete stoppage at B and no leakage 
would give a horizontal grade-line through A. Leakage through the 
overlying strata, or flow through many wells as at E, will reduce the 
pressure and consequently lower the grade-line to AEC. The local 
effect of wells upon each other is more fully discussed in Chapter XIV. 

96. Use of the Word “ Artesian.’ ’—The term “artesian” was 
formerly applied exclusively to flowing wells and is derived from the 
word “Artois,” the name of a province in France where such wells 
were first extensively bored. More recently, however, the term has 
come to be applied in a broader sense, according to which an artesian 
well may be defined as one in which the water is drawn from a porous 
stratum underlying a relatively impervious one and so located that the 



) -) > 








IOO 


GROUND- WA TER . 


contained water, drawn from a distant elevated outcrop, naturally 
exerts more or less pressure upon the overlying cover. Water will rise 
in such wells, but whether it will overflow depends much on local con¬ 
ditions, such as elevation of surface, and nearness of other wells. 
Many wells once flowing have ceased to flow owing to increased 
draught by others, and wells but a few hundred feet from others sunk 
to the same stratum will exhibit variations in this respect; but it is still 
convenient to call all such wells artesian, and the water artesian water. 

97. The Character and Inclination of the Strata, both of the porous 
stratum and the impervious cover, largely determine the capacity and 
usefulness of the artesian area. The important water-bearing forma¬ 
tions of an artesian character belong to the sedimentary rocks, but 
small areas of considerable local importance are met with in the drift 
formation. The water-bearing stratum is most often a porous sand¬ 
stone, although artesian water is also obtained from limestone and in 
many places from extensive strata of loose uncemented material. 

The overlying impervious strata usually consist of clays and shales, 
these being practically impervious except where fissured. Probably 
some leakage always takes place through such strata; but a condition 
favorable to small leakage is the existence of an elevated country 
between the outcrop and the area where wells are practicable. In such 
a case the ordinary ground-water level is likely to be above the 
hydraulic grade-line of the artesian basin, and the leakage would then 
tend to be into rather than out of the confined stratum. 

To be of most value the inclination of the beds of an artesian forma¬ 
tion should not be great, a steeper inclination than is necessary to 
furnish a good covering being disadvantageous. A small inclination 
furnishes a wide percolation area at the outcrop, and at the same time 
the area is large over which the stratum can be reached by wells of 
practicable depth. Thick strata give proportionately large percolation 
area and great carrying capacity. 

It often occurs that water is obtainable from two or more parallel 
strata. In such cases the lower usually furnishes the higher head, the 
outcrop being more remote and at a higher elevation. 

98. Capacity.—Except in the case of very limited areas, the 
capacity of an artesian source as a whole is a question of little impor¬ 
tance where it is to be used only for water-supply purposes in towns 
widely separated; for the total amount of water capable of being drawn 
from porous rock strata, often hundreds of feet thick and having an 
outcrop of hundreds or thousands of square miles, is ordinarily very 
great as compared to any possible demands for such purposes. The 



CAPACITY OF ARTESIAN AREAS. 


ior 


problem is rather one concerning the number and arrangement of wells 
to furnish a given quantity, a question which is discussed in Chapter 
XIV. 

In localities where wells are extensively used for irrigation purposes 
the total capacity of the source becomes a serious question, as is already 
the case in some portions of the West. 

The total possible yield of an artesian source may be limited either 
by the rainfall and percolation on the outcrop or by the carrying 
capacity of the strata. With the slight slopes and broad outcrops 
commonly occurring, the carrying capacity will probably determine the 
maximum yield, while with steep slopes and small outcrops the water 
may be drawn out faster than it flows in. 

The velocity of flow through the pores of rock formations is neces¬ 
sarily extremely slow on account of the great resistance offered. In 
many cases, no doubt, fissures and other openings of a large size rela¬ 
tive to that of the pores of the stone add very greatly to the carrying 
capacity of a rock stratum. In a sandstone formation such are not so 
likely to be of great influence as in the case of limestone, where indeed 
they may be the controlling factors in determining the capacity. 

99. Some rough calculations relating to the flow through thick porous 
strata may be of value in suggesting the possible limitations in the carrying 
capacity of sandstones and of strata of loose material. 

The Potsdam sandstone of northern Illinois and southern Wisconsin has 
a thickness estimated at from 700 to 1200 feet, and a width of outcrop in 
Wisconsin of 40 to 60 miles, or about 250 times its thickness. The percola¬ 
tion with a rainfall of about 35 inches may at the very lowest be taken at 
5 inches per year. Assuming a porosity of 20 per cent, this would fill the 
rock to a depth of 25 inches vertically, or a horizontal length of the stratum 
of 25 X 250 = 6250 inches, or 521 feet. Now the rate of flow depends upon 
the available head or hydraulic slope, which in the region here considered 
would not, even with the use of deep-well pumps, exceed 3 or 4 feet per 
mile. Assuming the resistance to flow to be equal to that in a fine sand of 
o. 1 mm. size (it is probably much greater),* the velocity would be, according 
to the table on p. 92, equal to 82 X feet per day, or about 22 feet per 

year, a very much less rate than that of the percolation. If the material were 
a very coarse sand of a size of 0.5 mm., the carrying capacity would, under 
the assumed conditions, be about equal to the rate of percolation. 

In some basins the possible slopes are somewhat greater than in the 
example given, but it will seldom be found that artesian areas are likely to be 
limited in supplying capacity by the want of percolation. 

The actual quantity flowing through a given cross-section may be roughly 
estimated in the same manner as for any other ground-water stream. In the 


* Some experiments by King on the flow of water through Madison sandstone 
indicate a resistance to flow equal to that in a sand of an effective size of about .01 
to .03 mm. See Nineteenth Annual Report U. S. Geolog. Survey, p. 140. 




102 


GRO UND- WA TER. 


case above discussed the flow would be from Table No. 22, p. 94, equal to 
4 


1.2 X 


52.8 


= 0.091 gallons per day per square foot of cross-section, or for a 


section 1 foot in width and 800 feet deep it would be about 73 gallons per 
day. The quantity flowing per mile in width would therefore be about 
400,000 gallons per day, and this would represent the maximum delivering 
capacity of a line of collecting-works of indefinite length. For isolated 
groups of wells the flow is lateral as well as in the direction of the general 
slope, and the capacity is relatively very much larger. In view, however, of 
the great distances over which large draughts affect the pressure in this area 
it is doubtful if the flow is much greater than the above figure. 


100. Predictions Concerning Artesian Wells.—The question of the 
existence of water-bearing strata at any point, their character and 
depth, and the location of outcrops, is a geological one; and where full 
information on this point has not been gained by the sinking of wells 
or by borings, a geologist familiar with the region in question should 
be consulted. Much money has often been wasted in fruitless attempts 
to obtain water in areas and at depths where none could be expected, 
and frequently such work has been carried on contrary to the advice 
of experts. 

The pressure which will exist in a well is a question of hydraulics. 
With a knowledge of the pressure in neighboring wells, and of the 
surface topography and elevation of outcrops, a fairly close estimate of 
pressure may be made. 

The questions of percolation, freedom of flow, and capacity cannot 
of course be very closely determined, but a careful consideration of the 
principles of hydraulics, which govern here as elsewhere, will at least 
enable one to avoid the absurd estimates which are sometimes made 
and which lead to disastrous results. 

In the construction of wells it is important to preserve samples of 
the borings, as it is largely through these that a knowledge of the 
geology of the region is acquired. Chemical analyses of the water are 
also a valuable aid in identifying strata. 

101. Important Artesian Areas in the United States .—The Atlantic and 
Gulf Coast Region. —One of the most extensive and important artesian-well 
areas in the United States is that which borders the Atlantic Ocean and Gulf 
of Mexico, extending from Long Island on the north to Texas on the south. 
Along the Atlantic coast it will average perhaps 100 miles in width, but along 
the Gulf it broadens out, extending up the Mississippi valley as far as the 
Ohio River, and in Texas it has a width of 200 to 300 miles. 

The several strata in which water is found belong to the Cretaceous forma¬ 
tion. They outcrop along the foothills of the higher country to the west and 
north, dip towards the ocean at a considerable slope (20 to 40 feet per mile 
along the Atlantic coast), and presumably have their lower outcrop in the 



IMPORTANT ARTESIAN AREAS IN THE UNITED S 7 ATES. IO3 


deeper ocean many miles from shore. Their connection with the ocean is 
indicated by the occurrence of ocean springs as already noted (Art. 92), and 
by the effect of the tides upon the pressure in certain wells, it being stated 
that at Pensacola the water-level in wells located several feet above sea-level 
varies from 6 to 10 feet as a result of tidal influence.* 

Fig. 22, p. 99, is a section showing arrangement of strata typical of this 
region. The conditions here are evidently very favorable for artesian wells, 
and the various water-bearing strata furnish an exceedingly valuable source of 
water-supply for the cities of this region that otherwise could procure pure 
water only at much cost. Among the cities which get their supply from this 
source are Savannah, Charleston, Jacksonville, St. Augustine, Key West, 
Memphis, Galveston, and Fort Worth, besides a large proportion of the ether 
towns in Florida, Mississippi, and Texas. Many wells have also been sunk 
in Long Island, New Jersey, Delaware, Maryland, and in the city of Phila¬ 
delphia. 

102. Artesian Areas in the West. —Another very important artesian area, 
noted for its high pressures and the great number of wells, is that of the 
James River valley in eastern North and South Dakota.t This area is 
supplied chiefly from the Dakota sandstone, a formation belonging to the 
Cretaceous. It outcrops along the slopes of the Black Hills and the Rocky 
Mountains at altitudes of 3000 or more feet above sea-level, furnishing a 
percolation area estimated at about 14,000 square miles. From there it 
descends beneath the more recent formations of the plains, again ascends 
slightly, and outcrops at its southeastern edge along the Missouri and Sioux 
rivers at an elevation of about 1000 feet. Farther to the north the edge of 
the stratum is covered, and the waters are there largely prevented from escap¬ 
ing. The result is that wells sunk to this stratum at points where the surface 
is low, as in the James and Missouri river valleys, will have high pressures 
(these are in some cases as high as 150 pounds per square inch static 
pressure), but towards the south and east the pressures rapidly fall off. Fig. 
23 is a section through South Dakota showing the arrangement of the strata. J 


BZocR ZZZZZs 


Sea LereZ 

Fig. 23.—Section through the Dakota Artesian Area. 

The report of Mr. Dart on gives a very instructive map showing the reduc¬ 
tion of pressure towards the eastern outcrop. The hydraulic slope amounts 

* Trans. Am. Soc. C. E., 1893, xxx. p. 695. 

f See report by N. H. Darton in U. S. Geolog. Survey, 1895-96, p. 603. 

% From U. S. Geolog. Survey. 1895-96, p. 611. 





1 

I 

I 

\ 



£ 






^ ZA/ocene CZa/j.? 

<0 

1 





\ 5 aAoZzr Sanc/stone 















.(04 


GRO UNO - WA TER. 


in general to from 4 to 6 feet per mile, which agrees fairly well with the slope 
from outcrop to outcrop. The estimated number of wells in this basin in 
1896 was 400, of which 350 were flowing wells. The total estimated yield 
was 232 cubic feet per second. The water is used for irrigation, water-supply, 
and power purposes. 

This same Dakota sandstone is the source of supplies over small areas in 
Nebraska, Kansas, and Colorado, while still other strata in more recent 
formations furnish artesian water in many places of the Western plains. 
Among the Rocky Mountains and in California are also many basins where 
artesian conditions are found. One such is shown in Fig. 18, p. 88. 

In 1890 there were altogether about 9000 artesian wells in the western 
part of the United States, located for the most part on farms for water-supply 
and irrigation purposes. Of this number over 3000 were located in Cali¬ 
fornia. * 

103. The Artesian Area in the Upper Alississippi Valley .—A large area, 
mentioned on p. 101, in which artesian water is extensively used for town 
supplies is that in northern Illinois, eastern Iowa, and southern Wisconsin. 
Here the water is furnished by several strata, chief of which are the St. Peter 
and the Potsdam sandstones. Fig. 24 is an approximate north and south 
section through central Wisconsin showing the general arrangement of the 
water-bearing strata.f The collecting area of the Potsdam strata is estimated 
at 14,000 square miles, while that of the St. Peter is only 2000 to 3000. 
These strata dip deeply below the surface in southern Illinois, and are there 
beyond reach. They also dip both eastward and westward from the section 



Fig. 24.—Section through Northern Illinois and Southern Wisconsin. 

shown. The slope of the surface of the ground is quite small, and the avail¬ 
able head and the quantity obtainable are therefore rather limited. At 

* Eleventh Census. Report on Irrigation by F. H. Newell, 
f From a paper by D. W. Mead, Jour. Assn. Eng. Soc., 1894, xm. p. 396. 
























LIT ERA TURK. 


105 


Chicago the available head originally was about 100 feet, but the draught has 
been so great that now the wells seldom flow, and the exhaustion is felt for 
several miles distant. 


LITERATURE. 

1. Thiem. Der Versuchsbrunnen fiir die Wasserversorgung der Stadt 

Miinchen. Jour. f. Gasbel. u. Wasservers., 1880, p. 156. 

2. Chamberlain. The Requisite and Qualifying Conditions of Artesian 

Wells. Report U. S. Geolog. Survey, 1883-84, p. 127. A com¬ 
prehensive treatment of the subject. 

3. Thiem. Neue Messungen natiirlicher Grundwassergeschwindigkeiten. 

Jour. f. Gasbel. u. Wasservers., 1888, p. 18. 

4. Harrison. On the Subterranean Water in the Chalk Formation of the 

Upper Thames and its Relation to the Supply of London. Proc. 
Inst. C. E., 1890, cv. p. 2. 

5. Artesian-well Practice in the Western United States. Compiled from a 

Government Report. Eng. News , 1891, xxv. p. 172 et seq. 

6. Stearns. The Selection of Sources of Water-supply. Jour. Assn. Eng. 

Soc., 1891, x. p. 485. 

7. Report of the Artesian and Underflow Investigation, 1893, Senate Doc. 

No. 41. Relates to the ground- and artesian water of the plains. 

8. Salbach. Experiences had during the last Twenty-five Years with Water¬ 

works having an Underground Source of Supply. Trans. Am. Soc. 
C. E., 1893, xxx. p. 293. 

9. Friihling. Handbuch der Ingenieurwissenschaften. Leipzig, 1893, in. 

Band, Abteilung I, 2. Halfte, pp. 189-212. 

10. Lubberger. Die Quellenbildung in den Yerschiedenen geologischen 

Formationen. Jour. f. Gasbel. u. Wasservers., 1894, p. 269. 

11. Mead. Hydro-geology of the Upper Mississippi Valley and some of the 

Adjoining Territory. Jour. Assn. Eng. Soc., 1894, xm. p. 329. 

12. Lueger. Die Wasserversorgung der Stadte. Darmstadt, 1895, Abteil¬ 

ung 1. Contains much matter relative to ground-water; also a 
large number of references. 

13. The Development of Percolating Underground Waters. Eng. News, 

1895, xxxm. p. 116. 

14. Maitland. The Geological Structure of the Extra-Australian Artesian 

Basins. Proc. Royal Soc. of Queensland, vol. xn., Apr. 17, 1896. 
Relates to the artesian basins of the United States. 

15. Hawes. Utilizing a Spring as a Source of Water-supply for a Town. 

Jour. New Eng. W. W. Assn., 1896, xi. p. 156. 

16. Darton. Artesian-well Prospects in the Atlantic Coastal Plain Region. 

Bulletin No. 138, U. S. Geolog. Survey, 1896. 

17. de Varona. History and Description of the Water-supply of the City of 

Brooklyn, 1896. Brooklyn Dept, of City Works. 

18. Gilbert. The Underground Water of the Arkansas Valley in Eastern 

Colorado. Report U. S. Geolog. Survey, 1895-96, Part II. 

P- 557 - 

19. Leverett. The Water Resources of Illinois. Report U. S. Geolog. 

Survey, 1895-96, Part. II. p. 701. 

20. Darton. Reports on the Artesian Areas of the Dakotas. Reports U. S. 

Geolog. Survey, 1895-96, 1896-97. 


106 GRO UND - WA TER. 

21. Leverett. The Water Resources of Indiana and Ohio. Report U. S. 

Geolog. Survey, 1896-97, p. 419. 

22. Orton. The Rock Waters of Ohio. Report U. S. Geolog. Survey, 

1897-98, p. 633. 

23. Barton. Report on the Geology and Water Resources of Nebraska 

West of the One Hundred and Third Meridian. Report U. S. 
Geolog. Survey, 1897-98, p. 719. 

24. King. Principles and Conditions of the Movements of Ground-water. 

Report U. S. Geolog. Survey, 1897-98, pp. 67-294. 

25. Slichter. Theoretical Investigation of the Motion of Ground-water. 

Report U. S. Geolog. Survey, 1897-98, pp. 295-384. Contains 
bibliography. 


ist 




*r:' 


B. QUALITY OF WATER-SUPPLIES. 

CHAPTER VIII. 

EXAMINATION OF WATER-SUPPLIES. 

104. Scope and Extent of Examination. —The most important ex¬ 
amination of water is that which is made to determine its potableness 
and wholesomeness. Attention should of course be given to a water- 
supply from other points of view, but the relation to disease-dissemina¬ 
tion is of paramount interest. 

In determining by means of a sanitary analysis whether any water 
is suitable as a public supply, various methods have been instituted as 
knowledge regarding these problems has been broadened. None of 
these methods, however, that have yet been introduced are wholly 
satisfactory, and the subject of sanitary water-analysis is far from being 
reduced to terms of mathematical accuracy. One prominent reason 
for the unsatisfactory results that are frequently found in analytical 
work is that many of the determinations apply only indirectly to the 
presence of specific disease organisms. This indirect relation therefore 
raises a question that must be interpreted anew in each individual 
instance. It calls for a discriminating judgment on the part of th^ 
analyst. In fact the data which he collects do not answer definitely 
and decisively the question as to the purity or pollution of a supply,. 

, but, as Mason has well expressed it, it assists his judgment in inter- 

I 

preting these data. 

105. Necessity of Full Data in Interpreting Conditions. —Concerning 
this phase of the water-analyst’s work there is a great deal of miscon¬ 
ception. Many people think that the withholding of all data as to the 
origin and local conditions surrounding the supply in question will 
enable the analyst to arrive at an unbiased opinion. Some in fact think 
that such a procedure is necessary to test his expert skill. They look 
upon a water-analysis as something similar to an assayer’s test for gold, 

something which can be positively determined. But when there is 

107 


io8 


EXAMINATION OF WATER-SUPPLIES. 


taken into consideration the wide range that may exist in waters from 
various sources, and how the analytical results obtained in such exam¬ 
inations will of necessity be interpreted differently in samples coming 
from different regions, it is manifestly impossible for the analyst to 
arrive at any satisfactory judgment unless he is more or less familiar 
with all of the data that are intimately related to the case. The char¬ 
acter of the stratum from which the supply is derived, the possibility of 
pollution, and the nature of the same, the kind of water, the conditions 
under which the sample has been secured and kept are all questions 
concerning which he should have full and explicit knowledge. Of 
course it may be possible in extreme cases, as with badly polluted or 
exceptionally pure waters, to determine their nature with certainty 
from a mere examination, but in the great majority of cases where the 
conditions are less pronounced, his judgment may be at fault because 
he is kept in ignorance of local conditions. A sample which would 
be regarded as satisfactory for a surface-water might be condemned 
from a biological standpoint if from a well, while the chemist would 
frequently reverse the conditions in testing certain artesian and surface 
waters. The case has been well compared to the physician who is 
able to diagnose any malady by an examination of the urine alone, or 
in some cases by an inspection of even a lock of hair. Such a 
diagnosis would have but little worth against the judgment of one who 
had studied the case at first hand. This should also be the position of 
the analyst. He should be able to inspect the local surroundings, as 
these frequently give evidence that may be of more value than the 
analytical data secured. If not able to secure the data at first hand, 
as full information as possible as to these facts should be furnished him. 

106. Collection of Samples. —The results obtained in the analysis of 
waters are frequently misinterpreted because of errors in sampling. It 
is necessary in this, as in all analytical work where reliance is to be 
placed on the results obtained from an examination of a comparatively 
small amount of material, to have a representative sample; not only as 
to its composition, but as to subsequent changes that may take place 
in same. In sanitary water-analysis the conditions are not as they 
would be in a mineral analysis of a rock or an ore. The substances for 
which search is to be made are for the most part living things, or the 
products of vital activity. Generally a water is not in stable equilib¬ 
rium, but is constantly undergoing changes which, if they occur 
before the analysis is made, may markedly affect the interpretation 
that might be given to the results. 

In taking samples for chemical or bacteriological purposes, certain 


SAMPLES POP ANALYSIS. IO9 

requirements must be observed that are somewhat different for the two 
purposes mentioned. 

107. Samples for Chemical Analysis. —For a chemical sample take 
a glass-stoppered bottle of about one-half gallon capacity.* Rinse out 
the same thoroughly so that it is free from dust or dirt. If it is impossi¬ 
ble to secure a bottle having a glass stopper, one fitted with a new cork 
may be used, but it should be very thoroughly rinsed before using. 
Fill the bottle nearly full with water, leaving a small bubble of air for 
expansion. To protect the mouth of bottle in transit, tie over same a 
piece of cloth. The cork should not be sealed in by using sealing-wax 
or paraffin. 

Great care should be observed to secure a representative sample. 
If from a well, the water should be pumped out so as to remove that 
which has been standing in the pipe. In a dug or open well it may 
even be preferable to pump out enough so as to remove at least a part 
of the quantity originally present in the well and thus allow a fresh supply 
of ground-water to flow in; although in cases of surface pollution the 
withdrawal of the water in the well diminishes the amount of polluted 
matter. If sample is taken from a surface supply, the bottle should be 
plunged beneath the surface before removing the stopper, so as to prevent 
the entrance of dust-particles and other floating impurities. Care should 
also be taken not to draw the sample from too near the bottom. 

108. Samples for Bacteriological Analysis. —For a bacteriological 
analysis still greater care must be taken in order to secure a represen¬ 
tative sample; and also to lessen the changes that quickly occur in the 
germ-life in a water. As ordinary glass receptacles always contain 
more or less bacteria adhering to the inner wall, it is necessary first to 
destroy these even after the bottle has been thoroughly cleaned. This 
is done by baking in a dry sterilizer (hot oven) at a temperature of 
about 280-300° F. for one hour, or steaming in a steamer at 212° F. 
When facilities are not at hand for sterilization by heat, the adherent 
germ-life can be destroyed by rinsing out the flask with chemical disin¬ 
fectants (corrosive sublimate, o. 1 per cent solution, carbolic acid, 5 per 
cent, or dilute mineral acids). It is then necessary of course to remove 
all trace of the disinfectant, which can be easily done by rinsing out 
the bottle at least four times with the water to be sampled. 

Every endeavor should be taken to exclude the influence of extrane¬ 
ous factors, and in a bacterial test these are much more numerous and 
exert a more profound effect than in chemical work. In a surface- 


* For a full mineral analysis five gallons is generally taken. 




110 


EXAMINATION OF WATER-SUPPLIES. 


water the influence of land contamination should always be considered. 
Samples taken from a stream after a rain where any turbidity has been 
produced will not be representative of normal conditions. In taking 
samples from wells, the pump and pipe should be thoroughly washed 
out, as bacterial growth generally occurs in water standing in the same. 
Preferably bacterial cultures should be made immediately after the 
sample of water is secured, as a marked change occurs in the germ 
content of water stored for a period, especially if temperature is rather 
high (135). This multiplication is less in tightly stoppered glass 
bottles than in those closed with cotton, and is less in full bottles than 
those partially filled. To lessen these changes as much as possible 
where it becomes necessary to transport samples any considerable dis¬ 
tance, they should be packed in ice, in which condition growth will be 
greatly retarded. Not infrequently in samples so treated there is a 
diminution to be noted. 

The bottles used to collect bacteriological samples do not materially 
differ from those employed in securing chemical samples, except that 
generally a smaller quantity of water will suffice, unless it is desired 
to filter a large amount through a germ-proof filter (Pasteur) and in 
this way concentrate the bacteria. In taking samples from deep 
waters, special kinds of apparatus have been devised that permit of the 
securing of a sample uncontaminated from that of any other depth. 

109. Sanitary Analysis of Water. —Definite knowledge of a certain 
character is often desired as to the quality of water for different pur¬ 
poses (manufacturing, etc.), but these data do not fall primarily within 
the province of the sanitary engineer. A sanitary analysis is the study 
of a water with the view of determining whether it now contains, has 
contained, or is likely to contain, anything which is detrimental to public 
health. Not only must potable water be free from any taint of sus¬ 
picion that would indicate dangerous pollution, but, at the same time, 
water should not be objectionable in taste and appearance. More¬ 
over, water-supplies must furnish water that is suitable for laundry and 
general domestic use, although this is not strictly a sanitary considera¬ 
tion ; but inasmuch as a supply must cover all purposes for which water 
is commonly used, this must also be considered. 

It is a notorious fact that the majority of people mainly judge of 
the quality of a water by its taste and appearance. If it is clear and 
sparkling and is fresh in taste, they will use it without question, caring 
little as to the possibility of pollution with disease bacteria. Once let 
these physical conditions be altered and suspicion at once attaches itself 
to the supply. This deep-grounded opinion arises for the most part 


DETECTION OF POLLUTION BY ADDITION OF CHEMICALS. Ill 


from a rational conviction that wholesome water, especially that derived 
lrom the ground, is clear and sparkling and ought to remain so. If 
for any reason a change occurs, it signifies a variation in conditions— 
a state to which ground-waters of first quality ought not to be subject. 
While this rule applies universally to ground-waters in wells, it is not 
so pertinent to surface-supplies or waters in large distributing systems 
as in large cities. 

In determining the sanitary condition of a supply, a single analysis 
is of but little value, especially if this is made by one unfamiliar with 
local conditions. To be able intelligently to interpret conditions with 
any marked degree of accuracy, analyses should be conducted at fre¬ 
quent intervals, in order to determine the stability of the chemical and 
biological composition. A water-supply subject to sudden and con¬ 
siderable fluctuations in these respects is generally one that should be 
regarded as suspicious, at least until the cause of such variation is satis¬ 
factorily explained. 

no. Detection of Pollution by Addition of Chemicals.—Not infre¬ 
quently a simple qualitative test that can be readily applied by the 
non-expert is of considerable service in detecting a possible polluted 
condition in a water-supply. This is generally done by the addition 
of some chemical substance to the source from which pollution is possi¬ 
ble and then determining whether the same reappears in the water- 
supply. For this purpose a number of different chemicals are used. 
Those most readily recognized are substances having a marked taste 
or appearance. 

Nordlinger recommends for this purpose saprol, which tastes like 
naphtha and is so penetrating that its odor can be readily recognized 
in proportions of I : 1,000,000, and by taste in solutions of I : 2,000,- 
000. Some of the anilin dyes, as fluorescein, often color the water in 
such dilute solutions that a change in color will be recognized even 
after filtering through a deep stratum of soil. 

Trillat*has recently experimented with a large number of these 
dyes and finds that fluorescein dissolved in alcohol and diluted with 
5 per cent ammonia solution can be detected by means of a fluoroscope 
in proportions of 1 : 2,000,000,000. The fluoroscope used is a tube 
of white glass three or four feet long and one-half inch in diameter, 
closed at one end with a rubber cork. In such an apparatus natural 
vvaters have a somber blue color which changes to a clear green if 
luorescein is present. This dye possesses the evident advantage of 


* Ann. Past., 1899, XIII. p. 444. 



112 


EXAMINATION OF WATER-SUPPLIES. 


not being precipitated by the soil ingredients, a reaction that readily 
occurs with most anilin dyes brought in contact with calcareous soils. 

Where chemical methods can be employed the use of readily solu¬ 
ble salts as, NaCl (common salt), permits of ready recognition. Salts 
of lithium are sometimes employed. These admit of detection in 
inappreciable quantities if the water is examined by the aid of a spec¬ 
troscope. It does not necessarily follow because these soluble salts 
reappear in a water that organisms and dangerous pollution would 
likewise find its way through the soil for an equal distance, for the 
filtering power of the soil if free from actual channels would be such as 
to remove suspended particles, even no larger than bacteria, while salts 
in solution would pass through soil by diffusion; but nevertheless these 
methods are of service in showing whether the possibility of danger 
exists. 

in. Various Analytical Methods. —In examining a water as to its 
suitability for public use, four different kinds of tests can and should be 
applied. These are as follows: 

Physical examination. 

Chemical examination. 

Bacterial examination. 

Microscopical examination. 

The respective value of these independent analytical methods 
differs much in various instances, yet in the examination of most waters 
all of them have a distinct value. The judgment arrived at as a result 
of these tests should be interpreted in the light of an actual inspection 
of surroundings, if possible. More and more, the experienced sani¬ 
tarian is coming to regard an ocular inspection as the final court of 
appeal to which all analytical conclusions should be referred. 

112. Value of Different Methods. —Naturally the physical tests as to 
the character of a water have been noted for the longest period. By 
the aid of the senses any one can detect in water an abnormal appear¬ 
ance, odor, or taste, if it is at all pronounced. If such obtains, this is 
generally sufficient to discredit the reputation of the supply. 

With the determination of the relation that exists between various 
water-borne diseases and human fecal matter, the chemical methods 
of examination were gradually devised. These have been slowly per¬ 
fected, so that at the present time they permit of the recognition of a 
larger number of factors that affect the value of a water than is to be 
determined in any other single way. But even the chemical method 
of examination is largely an indirect method of analysis. The presence 
of nitrites or chlorine in considerable quantities in a water is not a 


VALUE OF DIFFERENT METHODS. 113 

source of disease in and of itself, but under natural conditions a water 
revealing the presence of these substances in large quantities is generally 
one that has been polluted with organic matter, possibly of fecal origin. 
So generally has this indirect relationship been determined that the de¬ 
tection of considerable quantities of such chemical compounds as these 
is regarded as sufficient evidence of sewage pollution. It must of course 
be kept in mind that sewage from healthy sources may be diluted to 
such an extent as to be comparatively harmless; but the fact remains 
that such sewage may suddenly become detrimental by reason of dis¬ 
ease bacteria gaining access to the same, a condition which is of course 
readily possible if even dilute sewage was to be tolerated in any supply 
used for potable purposes. 

Again, a distinct value of the chemical method of analysis is that it 
tells something of the previous history of the water. If nitrates are 
present under certain conditions, it shows that organic matter has had 
access to the water and has undergone the decomposition changes 
incident to such material. This may therefore represent a condition 
of past pollution. 

Unfortunately, on the other hand it is not always possible to decide 
by the chemical method as to the origin of such organic decomposition 
products; whether they are associated with human or animal sources 
or perhaps attributable to vegetable decay. Often the chemical analy¬ 
sis is extended to include incrusting constituents, a determination of 
the alkalinity, the carbon dioxid and the iron dissolved in the water. 
Ordinarily, though, these have no special sanitary significance, and are 
made to determine the character of the water from other points of 
view. Under certain conditions, as in filtration work where coagulants 
are used, the determination of alkalinity is of sanitary importance as a 
basis for the addition of the coagulating agent. 

Inasmuch as the direct causal agent concerned in the production of 
disease by the use of impure water usually belongs to the bacteria, it 
would be reasonable to suppose that a bacteriological examination 
would be a direct method of determining the quality of water, and it 
would therefore possess a value that does not obtain in the use of any 
of the indirect methods. This hope, however, has been only imper¬ 
fectly realized as yet; for, in the main, these methods do not often 
consist in a direct search for the specific disease organism, but in appre¬ 
hending the conditions that might permit of the recognition of sewage 
pollution or the possibility of infection. Therefore these methods of 
examination as now used are also to be considered as indirect. This 
course is rendered necessary by reason of the fact that disease germs 


114 EXAMINATION OF WATER-SUPPLIES. 

rarely exist in any water in sufficient numbers for any considerable 
length of time so that they can be readily recognized; whereas if they 
find their way into water through the introduction of fecal discharges,, 
this evidence will be apparent for a longer period of time. The bac¬ 
teriological tests are also a more sensitive measure of the changes in 
the condition of the water. By carefully controlled quantitative 
estimates it is thus possible to detect variations in composition that 
would remain unobserved if sole reliance were placed on other analytical 
methods. Again, the bacteriological method offers by far the most 
accurate way to determine the efficiency of filter practice. 

The microscopic examination of water does not so much concern 
itself with a determination of whether sewage or the possibility of such 
pollution is actually present or not, as it does with the character of the 
minor organisms of a vegetable and animal nature. Some of these not 
infrequently cause bad odors and tastes in waters, but for the most part 
they do not have any other sanitary significance (183). Few are more 
or less distinctive of polluted waters, and hence their recognition is of 
value in this connection. 

PHYSICAL EXAMINATION OF WATER. 

To the sanitary engineer as well as the non-technical individual, 
the physical tests applied to any water are of considerable importance, 
as frequently an acute sense will be able to determine by these means 
a water that is unsuitable for use. 

113. Color.— A water to be perfectly satisfactory as to its physical 
requirements should be colorless, free from any turbidity, undesirable 
odor or taste, and of sufficiently low temperature to be refreshing. 
Ground-waters are for the most part free from color, but some surface- 
waters, particularly those of swampy origin, are often highly colored by 
the soluble organic matter that is dissolved in them. The peaty waters 
of north England and a large number of the streams draining the forest 
areas of the United States and Canada are typical of this class. Water 
colored from this cause generally exerts no noticeable effect on the 
health of persons using it. 

In determining color, comparison with some arbitrary standard is 
usually made.* For this purpose several standards have been proposed. 
One of the earliest was to use the colors produced by the Nessler 
standards employed in the estimation of ammonia. With yellow 

* The following papers give a full discussion concerning the subject of color 
determination: Jour. Frank. Inst.. 1894, p. 402; Jour. Am. Chem. Soc., 1896, XVIII. 
pp. 68, 264, and 484; Jour. N. E. Water-works. Assn., 1898, XVJII. p. 94. 





PHYSICAL EXAMINATION OF WATER. 1 I 5 

waters, this standard was fairly satisfactory. A more recent and more 
satisfactory standard is made by comparing waters with dilute solutions 
of salts of platinum and cobalt. By varying the ratio of cobalt to platinum 
it is possible to simulate closely the hue of the natural water. The color 
is recorded in terms of the platinum, one part of the metal in 10,000 
parts of water equalling one unit. 

114. Turbidity —Waters drawn from surface sources, particularly 
from running streams, are often more or less turbid from the presence 
of suspended matter that finds its way into the drainage-streams by 
reason of the run-off. Depending upon the geological nature of the 
watershed, this turbidity may be sandy or clayey. If sandy, the actual 
amount of suspended matter may be quite large without making the 
water unsightly. On the other hand, if clay particles abound, a much 
smaller amount may render the water densely turbid. Sometimes 
these particles are so minute and of such a gelatinous nature that even 
after a long period of quiescence the water remains more or less 
cloudy. 

While turbidity in a water is generally due to the presence of 
inorganic matter, yet vegetable growths at times may render a water 
turbid. Such troubles are generally seasonal, due to the increase of 
these vegetable forms during the warmer months. Algae, and particu¬ 
larly the diatoms, are most frequently concerned in such changes. In 
iron-containing waters, a turbid condition may be induced by the pres¬ 
ence of the iron-bacterium, Crenothrix (196), or by simple chemical 
oxidation of the ferrous salts to ferric oxid. Lake waters, such as those 
of our Great Lakes, are relatively free from turbidity, except as dis¬ 
turbed by storms. Rivers draining forest areas are generally quite 
clear, although they may be colored from dissolved organic matter. 

The earlier methods of turbidity determination rested upon the 
weight of suspended matter present in the water, but, as Hazen says, 
this did not take into consideration the variation in size of particles; and 
as turbidity in a water affects primarily its appearance, optical rather 
than gravimetric methods of determination were needed. 

Various devices have been suggested. The simplest and most 
readily applied is the platinum-wire method, in which the turbidity is 
expressed by the depth at which a platinum wire 0.04 of an inch 
(1 mm.) is visible. A turbidity of 1.00 means that such a wire can 
be seen only one inch below the surface; if seen 10 inches deep, the 
turbidity would be o. 1. For densely turbid waters it is necessary 
to dilute with clear water before estimating the turbidity. A water 
having a turbidity of 0.02 would be observable on close inspection. 


EXAMINATION OF WATER-SUPPLIES . 


116 

Another method used is to employ a white disk. Whipple employs 
one 8 inches in diameter that is painted black and white alternately. 

115, Odor and Taste,— Normal waters should be relatively free from 
any pronounced odors or tastes. The naturally pleasant taste noted 
in good water is due in the main to the oxygen and C 0 2 dissolved' 
therein. Some waters, particularly spring-waters, may at times give 
forth an earthy odor due to the volatile substances absorbed from the 
upper soil layers. In other cases they may be so thoroughly impreg¬ 
nated with various mineral ingredients as to possess a distinct taste, as 
is the case with salt, iron, or sulfur springs. 

A considerable number of the lower plant and animal forms are 
able to affect the taste and odor of waters, especially open surface- 
waters. “Fishy,” “grassy,” and oily conditions are those most 
frequently noted. These odors are not attributable so much to the 
decay of organic matter as they are to the growth of certain odor-pro¬ 
ducing algae (183). To recognize more thoroughly the odor of water, 
it should be warmed to about 65° F., the bottle remaining tightly 
corked until the test is applied. 

116. Temperature.— From the standpoint of the consumer, the tem¬ 
perature of a water is considered of first importance. Naturally this 
condition is determined by the source of the supply. Surface-waters 
follow in general the atmospheric variations, but, owing to the high 
specific heat of water, they never show the range to be noted in the 
atmosphere. In winter, the temperature of water-supplies may almost 
reach the freezing-point, while in summer it frequently exceeds 8o° F., 
being as much too warm at this season as it is too cold for use in winter. 
In quite large and relatively deep bodies of water the temperature 
changes are not so marked. In deep lakes protected from strong wind 
action, the temperature of the lower stratum changes very slowly owing 
to the low conductivity of water; but in shallow waters the temperature 
coincides more closely with that of the mean atmospheric temperature. 

Ground-waters have a much more uniform and lower mean tem¬ 
perature than waters exposed to the air. At a depth of 40-60 feet, 
varying in soils of different composition, the zone of constant tempera¬ 
ture is reached and waters from this level remain quite uniform 
throughout the year, ranging from 48-52° F. If the temperature of 
the supply is subject to much fluctuation, and especially if it is above 
these limits, it indicates a supply of shallow origin. Very deep wells, 
as artesian supplies, frequently have a considerably higher temperature, 
due to the effect of the internal heat of the earth. 

Often a city supply that has a suitable initial temperature has its 




CHEMICAL EXAMINATION OF WATER. 117 

temperature raised to a point where it tastes insipid because of the 
shallow depth at which the mains are laid, or the long distance from 
source to place of consumption; but usually the temperature as deliv¬ 
ered to consumers depends mainly upon that of the source.* 

Generally the temperature of ordinary supplies derived from lakes 
Can be measured quite closely by lowering a thermometer in a vessel 
of considerable capacity. This can be withdrawn before it materially 
changes. For accurate determination Warren and Whipple + have 
devised an instrument known as the thermophone, which is practically 
an electrical thermometer of the resistance type. This instrument 
permits of the registration of the temperature at any depth. 

117. Chemical Reaction,—The chemical reaction of a water is usually 
slightly alkaline, due to the presence of calcium and magnesium car¬ 
bonates; in peaty waters the reaction is acid, caused by the vegetable 
acids here found (humic, geic, and ulmic). 

CHEMICAL EXAMINATION OF WATER. 

118. Purpose of Chemical Tests. —The chemical methods of water 
analysis do not seek to ferret out the presence of any specific disease- 
producing organism. A water may possibly be regarded as bad from 
a chemical point of view, and yet be wholly free from disease organ¬ 
isms, but under ordinary conditions the disease-germs that are dissemi¬ 
nated by polluted water-supplies generally find their way into the same 
through the medium of sewage. Under these conditions, then, the 
chemist does not test directly for any specific microbe, but for sewage 
pollution, present or past. This he does on the basis that a water- 
supply intended for human use should under no condition contain any 
evidence of fecal pollution. His aim, as Drown states, is to discover 
the origin and history of the nitrogen compounds in the water. 

The tests that the chemical analyst employs in passing judgment 
on che sanitary quality of a water are for the most part, however, 
methods that indirectly permit him to recognize the presence of living 
organisms in the water. The determination of organic matter by the 
loss in weight of total solids before and after ignition, the presence of 
nitrites and nitrates, the amount of oxygen consumed, the free and 
albuminoid ammonia present, are all of them directly related to organic 
matter of vegetable or animal origin. 

119. Expression of Chemical Data, —Much confusion exists in the 
interpretation of chemical data because no single standard is recognized 


* Exam, of Water, 1890, p. 675, Mass. Bd. Health, 
f Microscopy of Drinking-water, p. 55. 




/ 


11 8 EXAMINATION OF WATER-SUPPIIES. 

the world over in presenting the results of analytical work. The earlier 
method of giving number of grains per gallon * has been for the most 
part supplanted by the method of expressing the data either as parts 
per 100,000 or parts per million in weight, the evident advantage of 
the latter method being that no computation is necessary where weight 
is expressed in milligrams, as this gives parts per 1,000,000 when 
referred to a liter. + 

120. Interpretation of Chemical Data. —It is beyond the purpose of 
this book to take up methods of analysis, but the sanitary engineer 
should be able at least to interpret in a general way the results of such 
analyses. 

Desirable as it would be to have definite standards of water analysis 
that would apply to all waters, such are, nevertheless, impossible. The 
changing conditions under which various potable supplies occur make 
it z }together out of the question to have a standard that would be of 
general application. In the present state of the science there is even 
a lack of uniformity in interpreting results, some analysts placing more 
emphasis on one factor than on another. 

While a general standard of purity is not possible, many have 
advocated the adoption of local standards that embrace a definite 
geological formation in a restricted region. This standard of course 
could not apply to all classes of waters from even a single region, but 
would have to be limited to waters of the same origin, as wells, springs, 
or streams. 

121. Total Solids and Character of Same. —Ordinarily a water is 
examined in an unfiltered condition, but in certain cases it is necessary 
to differentiate between substances in solution and those held in sus¬ 
pension. The total solids of a good water, including both suspended 
and soluble matter, vary considerably, depending upon the geological 
formation. Well- and spring-waters are naturally much higher in 
soluble solids than surface supplies. 

The solids in a water are made up of mineral matter such as 
carbonates, chlorides, sulfates, etc., together with the organic matter of 
vegetable and animal origin. The inorganic ingredients determine the 
hardness of the water, a characteristic that is generally determined, but 
which is of more economic than sanitary importance. The hardness 

* Conversion Table. —To convert grains per Imperial gallon (parts per 70,000) into 
parts per million, divide by 7 and multiply by 100. 

To convert parts per million into grains per gallon, multiply by 7 and divide by 
100. 

f This standard is recommended by the Committee on Methods of Water Ex¬ 
amination appointed by the American Association for the Advancement of Science. 


1 




CHEMICAL EXAMINATION OF WATER. I 19 

in a water is temporary when it is caused by carbonates which are 
precipitated upon heating, while the sulfates and chlorides produce a 
permanently hard water. A water of moderate hardness is generally 
preferred by most people to soft water for drinking purposes. Not 
infrequently, waters are so hard as to be unsuitable for industrial as 
well as domestic purposes. In such cases they can be softened by the 
aid of chemical treatment (Chapter XXIII). 

* 122. Loss on Ignition, —If the evaporated residue obtained in deter¬ 
mining the total amount of solid matter is gradually heated to redness, 
the organic matter is driven off by degrees. If the ash is white, it 
denotes the presence of mineral solids, although the presence of iron 
will tend to discolor the ash. If much organic matter is present, 
it blackens and the peculiar smell inherent to vegetable or animal 
substances may often be detected. 

Peaty waters will naturally contain a considerable amount of 
organic matter, the presence of which may not be incompatible with 
good water. 

The relation between the weight of the total solids obtained by 
drying at 212° F. and the ash after ignition marks the amount of 
organic matter, but some mineral salts break up on being heated and 
so diminish the value of this determination. 

123. Chlorine. —All surface- and ground-waters contain chlorine in 
variable proportions, the majority of the chlorides existing in the form 
of sodium chloride (common salt). In certain regions which are under- 
lain with salt-bearing strata, as central New York and Michigan, the 
chlorine content of the ground-waters is of course high. Proximity to 
the ocean also increases appreciably the chlorine of unpolluted waters, 
both those of deep and surface character. This has been strikingly 
shown in Massachusetts and Connecticut, where a survey of these States 
has been made with reference to this point. The lines representing 
approximately equal amounts of chlorine, called isochlors, run, in 
general, parallel with the coast. They range from 24 parts per million 
on ocean-engirdled Cape Cod to .6 part per million in the northwest 
portion of Massachusetts. These data are very valuable in determining 
a local standard as to the normal condition of unpolluted waters of 
different regions. 

Chlorine is also a constant accompaniment of sewage and house- 
wastes, urine containing from 0.75 to 1 per cent of the same. The 
readiness with which this element percolates into the soil, and its 
stability, are such that it serves as a ready means of determining whether 
the ground-water is polluted with household or animal wastes. 


120 


EXAMINATION OF WATER-SUPPLIES. 


The presence of no more than normal amounts in a water is there¬ 
fore good evidence that it is unpolluted, but the converse of this does 
not necessarily mean pollution. Here is where the necessity of addi¬ 
tional data is evident as to the normal chlorine content of waters in the 
region under investigation. Excluding chlorine due to salt deposits 
and that derived from the sea, a high content generally means pollution 
with sewage or household wastes. Chlorine in itself, however, may 
be misleading, as it tells nothing of the time of pollution. Being solu¬ 
ble it percolates slowly into the ground, and it by no means follows 
that disease bacteria or any other harmful substance is capable of fol¬ 
lowing it. Pollution may have occurred at some previous date and the 
organic matter undergone complete oxidation, and yet the chlorine 
remains to tell of past pollution. 

In this way the soil of inhabited areas becomes gradually impreg¬ 
nated, so that the ground-water of such regions is generally much 
higher in chlorine than that from less thickly populated localities. 

The observations of the Massachusetts Board of Health indicate 
that 100 persons to the square mile will increase, on the average, the 
normal chlorine of a region about 0.5 part per million. Thresh’s* 
estimate for England is about 0.43 part per million for the same 
increase in population per square mile. 

124, Organic Matter. —Inasmuch as the really dangerous substances 
in a water from a sanitary point of view are organic in nature, the 
determination of this factor is of prime importance. The organic 
material in water may be of either animal or vegetable origin. Purely 
vegetable matter, as in peaty waters, may frequently be present in excess 
and still such waters be perfectly wholesome. That which is associated 
with human wastes is of course the most dangerous, but it is not easy to 
determine by chemical analysis the exact origin of the organic matter 
as to whether it is derived from animal or human sources. 

125. Free and Albuminoid Ammonia. —Inasmuch as the nitrogen 
content of organic matter throw's much light on the character of the 
same as to whether it is of animal or vegetable origin, a determination 
of this element in the form of free and albuminoid ammonia is of cr rea t 

o 

service in sanitary chemical analysis. In the decomposition of organic 
matter, more or less complex nitrogenous by-products are produced 
that are classed as albuminoid in character. In the more ultimate 
stages of this disintegration, the nitrogen appears in the form of am¬ 
monia which may unite with acids to form salts. These products are 
finally converted by other bacteria in nitrites and nitrates. 


* Pearmain and Moor, Chem. and Biol. Analysis of Water, p. 51. 





CHEMICAL EXAMINATION OF WATER. 


121 


Albuminoid and free ammonia therefore represent nitrogen in the 
earlier transition stages, and inasmuch as these products invariably 
accompany fecal matter, their presence in water is of sanitary signifi¬ 
cance. 

Waters may, however, contain considerable quantities of free 
ammonia under normal conditions and still be entirely wholesome, as 
in peaty moorland waters, in rain-water, and even in artesian wells.. 

In the case of many ground-waters the ammonia is probably due tc 
the reduction of nitrites and nitrates by reducing substances present in 
the soil. Albuminoid ammonia should not be present in such waters. 
If it is, it is indicative of surface pollution or imperfect filtration. The 
ratio between the free and albuminoid ammonia is of importance in 
judging of the character of the organic matter. Generally a high ratio 
between the albuminoid and free ammonia in connection with low 
chlorides and nitrates characterizes vegetable pollution; increased 
amounts of free ammonia with an excess of the chlorides, animal 
matter. 

Something as to the character of the organic matter present can be 
told, according to Smart, by the rate at which the ammonia is 
evolved, gradual evolution signifying fresh pollution, while rapid pro¬ 
duction shows the organic matter in a more advanced state of decom¬ 
position. 

The necessity for early analysis is to be observed in the change 
which the ammonias undergo in waters that are allowed to stand for 
some days, the free ammonia gradually being converted into nitrites 
and nitrates. The organic ammonia is more stable, but it, too, in 
time breaks down and passes into the “free” stage as a result of 
biological changes. 

126. Oxygen Consumption, —Another method of determining organic- 
matter is to find out how much oxygen is required to oxidize the matter- 
present in a water. Generally in a water deficient in unoxidized sub¬ 
stances, as ferrous salts, nitrites, etc., the carbon of organic matter 
readily takes up oxygen, so that a determination of this capacity for a 
standard length of time enables the amount of organic matter to be 
approximately determined. This is accomplished by using an acidified 
solution of potassium permanganate. Often two determinations are 
made; one for 10 or 15 minutes, in which the readily oxidized matter, 
as nitrites, ferrous salts, and sulfides, are acted on; the other for a 
number of hours, during which the less readily oxidizable organic 
matter will be acted on. Surface-waters carrying suspended matter, 
or peaty waters, also show a high oxygen-consuming capacity. 


122 


EX A MIX A IT OX OF WATER-SUPPLIES. 


127. Nitrites. —Nitrites represent nitrogenous matter in an inter- 
mediate stage of decomposition, and therefore their presence signifies 
present pollution with organic matter in which germ-life is active, and 
is, therefore, an unfavorable symptom in water if present in any con¬ 
siderable degree. This salt may occur as a result of the incomplete 
oxidation of ammonia products by the nitrifying organisms, or it may 
sometimes be formed by the reduction of the more stable nitrates by 
the denitrifying bacteria which abound in decomposing organic matter. 
Usually such substances are absent in good well-waters, but if present 
they may be due to reduction processes, the change often being accom¬ 
plished by such mineral substances as ferrous oxid. In such instances 
the existence of nitrites may have no sanitary significance, as they 
are not likely to be associated with disease-producing bacteria. The 
presence of high nitrites and high free ammonia is usually indicative 
of sewage pollution either in surface or subterranean waters. 

128. Nitrates. —These salts represent the ultimate, the final stage 
into which nitrogen is changed by the biological processes in soil and 
water. In this form nitrogen is more stable, and these salts therefore 
collect in the soil, subject only to leaching, and the use they play in 
the development of the green plant. Their presence therefore may 
indicate merely past pollution, without any present danger. Not 
infrequently deep wells may contain high nitrates without suspicion 
being cast on the quality of the water; but if associated with free 
ammonia or nitrites, it is evidence of incomplete oxidation. The 
higher nitrogen content of animal in comparison with vegetable matter 
is generally betrayed in the amount of nitrates present in a water. 

1290 Summary.—From the foregoing considerations it is manifestly 
impossible to determine the character of a water by the use of a single 
test. The substances that accompany sewage, which is primarily 
dangerous on account of the disease-producing micro-organisms that it 
may contain, are so frequently found in connection with waters that have 
had no opportunity for dangerous pollution, that the analyst must use 
the greatest care in interpreting the results of an analysis. Chlorine 
and nitrites as such, for example, are not dangerous to human health, 
but it is because these substances prevail in waters that are polluted 
with dangerous matter. If their presence was characteristic of sewage 
only, then the matter of sanitary water-analysis would be reduced to 
•.simple terms,.but unfortunately such is not the case. 

The most that a chemical analysis can do is to prove the presence 
of organic matter that may be a source of pollution. It throws no light 
on the question as to whether the same is actually disease-producing 


BACTERIAL EXAMINATION OF WA TER. 


123 


or not. Even though sewage is shown to have polluted a water, this 
does not prove it to be absolutely dangerous; but of course if the possi¬ 
bility of pollution is present, all it requires is the accident of disease to 
start an epidemic. The history of polluted waters is so uniformly in 
harmony with the view that typhoid is so distributed that, generally 
speaking, no further proof is required. (See Chapter X.) 

* 

BACTERIAL EXAMINATION OF WATER. 

130. Development of Methods. —Inasmuch as the specific organisms 
of disease which are the really dangerous and polluting elements in a 
water are for the most part included in that group of lower plant-forms 
known as the bacteria, it might naturally be thought that the bacterial 
examination of a water would quickly and satisfactorily solve the ques¬ 
tion as to the wholesomeness of any supply, but, for reasons cited before 
(112), such is not the case. In comparison with the chemical methods 
of investigation, the technique of bacteriological methods is of recent 
introduction, being based on the epoch-making discoveries of Koch 
made less than two decades ago. Considerable improvement has been 
made in the development of methods, but even yet analytical practice 
is not nearly as uniform as it is in chemical manipulation. Bacterial 
methods have, however, aided materially in the matter of sanitary 
interpretation, but both should be employed in analytical work. 

131. Scope of Bacterial Tests. —The information to be obtained by 
the various bacterial tests of waters is principally as follows: 

1. Detection of presence of sewage or foreign pollution which 
may or may not be associated with infective matter. In this respect 
the bacterial method embracing both quantitative and qualitative work 
is practically coordinate with the usual sanitary chemical analysis. 

2. Quantitative bacterial analysis affords a very sensitive measure 
for making comparative tests as to distance to which pollution can be 
traced in a stream or lake, to establish presence of leaks in submerged 
pipes and to study effect of external conditions ; in fact the determina¬ 
tion of many variations in quality. In this respect it is often a more 
accurate measure than a chemical determination. 

3. In the control of the operation of filters bacterial analysis is 
very much superior to any other method, for the reason that it deter¬ 
mines directly the number of organisms before'and after filtration. In 
a chemical analysis so many of the determinations are of substances 
in solution which readily pass a filter that will hold back the danger¬ 
ous suspended matter (bacteria). 


124 


EXAMINATION' OF WATER-SUPPLIES. 


4. The isolation and study of pathogenic organisms from waters. 
This is generally done by combining cultures on artificial media with 
animal experiments. 

132. Methods of Determining Bacteria. —The bacteria are altogether 
too small to permit of individual recognition by simple microscopic 
examination of water. Their number* and general character is 
determined by adding the water to be examined to various kinds oi 
culture media, i.e., food substances in which bacteria can readily grow. 
Then as each organism develops, a tiny aggregation of cells is produced 
which is made up of organisms that belong to a single species. Such 
a mass of germs is known as a “colony.” A “pure culture” is then 
made by transferring a bit of this colony growth to tubes filled with 
sterile culture media, on which there appears in due time the character- 
istic growth of the germ in question. For culture purposes gelatin or 
agart is used. Making a satisfactory culture medium requires con¬ 
siderable care, especially as to the proper chemical reaction of the 
same. Slight variations in this regard are the cause of wide differences 
in results, a condition which readily explains the discrepancies fre¬ 
quently noted between different observers. 

In studying the bacteria various liquid and other solid media are 
constantly made use of, for the purpose of differentiating species, but 
the technique of their preparation and use is a question that concerns 
the bacteriologist rather than the sanitary engineer. 

133. Quantitative Bacterial Analysis. —Although too much stress 
In the past has been laid on the simple quantitative enumeration of 
bacteria in a water as an index of its quality, yet, notwithstanding this, 
the determination of mere numbers when properly controlled gives 
considerable information concerning a water. It is wholly an erro¬ 
neous conception that the quality of a supply can be measured by a 
mere numerical estimate, for there are so many disturbing factors that 
modify this determination that as a standard it has no value. Improper 
selection of samples, slight possible contamination with unsterile sur¬ 
faces at time of sampling, development of bacteria in sample before 
cultures are prepared, slight variations in composition of media, differ¬ 
ent kinds of media, variation in incubation temperature, in moisture of 
culture-dish, the possible error due to small quantity of water tested, 

* This number is uniformly expressed in the number of organisms per cubic 
•centimeter (c.c.), which is approximately one-third of a teaspoonful. 

f Agar is a bacterial nutrient culture medium made from Japanese seaweeds. It 
possesses the property of melting at about 210° F., and remaining fluid until the 
temperature falls to ioo° F., when it solidifies. It can therefore be used advan¬ 
tage ously as a culture medium at blood temperature. 







BACTERIAL EXAMINATION OF WATER. 


125 


and numerous other conditions, all contribute to make a numerical 
estimate too delicate a measure. It is therefore impossible to propose 
a quantitative norm or standard, and pass or reject waters on such 
an arbitrary basis. 

Still the previous history of a water is to a large extent revealed in 
a bacterial enumeration of a properly handled sample. Waters that 
have come in contact with the bacteria-rich upper soil-layers normally 
contain a higher number than waters of subterranean origin. If then 
the normal condition of a water is known, a marked quantitative 
increase indicates pollution from some outside source. The germ con¬ 
tent of various waters noted in Chapter IX will indicate in a general 
way the normal condition, and will thus serve as a basis for comparison. 
Generally speaking, good waters have relatively few bacteria, but it 
does not necessarily follow that a water rich in bacteria is necessarily 
poor in quality. 

For comparative estimates the quantitative ' determination of 
bacteria is often more sensitive than any other method of testing. In 
studying the efficiency of filter operations, or the natural purification of 
a stream or lake polluted with sewage or surface drainage, this method 
is of great value, as in the case of the Toronto water-supply, where 
the intake-pipe was broken near shore and so permitted the entrance 
of water from the polluted shore region.* 

Where the natural variation in germ content between the two 
waters compared is marked this method is of avail, but its usefulness 
decreases as the normal bacterial contents of the compared samples 
approximate each other. 

134. Effect of Incubation Temperature on Growth. —The normal 
water bacteria are of course accustomed to a relatively low tempera¬ 
ture, that of the air, while those derived from the intestinal contents of 
animals and man thrive best at a temperature approximating the blood- 
heat. If water is incubated in agar at blood-heat or slightly above 
(98-100° F.), the major portion of the distinctively water organisms 
will be suppressed, whereas those species associated with fecal matter 
will find optimum conditions for development. This differentiation by 
means of heat can also be effectively combined with the addition of a 
fermentable sugar and an indicator, such as litmus, to the culture 
medium, making a physiological test of much value (139). 

135. Multiplication of Bacteria in Collected Sample. —If water sam¬ 
ples are allowed to stand at ordinary temperatures before cultures are 
made, the accuracy of quantitative determinations is much reduced. 


* Jour. N. E. Water-works Assn., June 1S96, p. 211. 





126 


EXAMINATION OF WATER-SUPPLIES. 


This is due to the very rapid growth of the bacteria in the water after 
sampling. Often the development in such cases is enormous for a few 
days, and then a marked decrease may occur. The following data on 
samples of filtered water from Zurich illustrate this condition: 

No. of Bacteria per c.c. 


Immediately after collection. 143 

After 24 hours’ standing.... 12,457 

•After 3 days’ standing. 328,543 

After 8 days’ standing. 233,453 

After 17 days’standing. 17,436 

After 70 days’ standing. 2,500 


In waters that originally contain a large number of bacteria, as in 
polluted streams or lakes, this development is not nearly as marked. 
In fact, Miquel holds that this distinction characterizes very pure and 
polluted waters. 

This fact has considerable bearing on the question of analyzing 
water samples from a distance. Unquestionably, for quantitative 
results it is preferable to make culture-plates at the time samples are col¬ 
lected, but frequently this cannot be done; in which case they should 
be maintained at low temperatures in full bottles during transportation. 
Frankland* has noted that in bottles closed with cotton stoppers 
growth was very marked, while in tightly sealed bottles filled completely 
with water practically there was no development. 

136. Qualitative Bacterial Analysis. —After all it is the character of 
the bacteria in a water that is of most importance. The presence of 
pathogenic species or those indicative of sewage pollution cannot be 
told by a numerical estimate, but requires a study of either the isolated 
organisms or the incubation of the water under such conditions as to 
encourage the growth of those forms that are associated with polluted 
supplies. In noting the qualitative characteristics of any water, 
advantage can be taken of the culture-plates prepared for the quantita¬ 
tive data to determine several points of value. 

137. Number of Species. —The bacterial flora of a water is of course 
subject to more or less change, due to variation in environmental fac¬ 
tors, but at any single time the number of species in an unpolluted 
supply, even though of surface origin, is not generally very large. 
Where pollution has arisen from the introduction of decomposing 
material rich in organisms, not only in number but often in kind, the 
number of species present will be increased. Some have placed an 
arbitrary limit on the number that ought not to be exceeded (Migula’s 
standard is 10), + but such conclusions cannot be drawn with safety. 


* Micro-organisms in Water, p. 234. 
f Prac. Bact., English trans., p. 167. 











BACTERIAL EXAMINATION OF WATER. 


127 


The gelatin-plate cultures afford the best medium for this differentiation 
of species. 

138. Significance of Liquefying Bacteria. —In growing on gelatin 
plates, bacteria are either able or unable to render gelatin fluid. 
Putrefactive organisms are often liquefying species, and hence an 
abnormally high percentage of liquefying colonies is considered 
undesirable in a water. Such a condition is certainly abnormal, but it 
is hardly possible to attach much specific importance to this finding, 
for all natural waters normally contain liquefying species, although they 
are usually much less numerous than the non-liquefying forms. 

The separation of individual species is generally made from the 
culture-plates prepared for quantitative work. Where the colonies on, 
gelatin or agar plates are separate from each other, pure cultures of the 
different forms should be made. It is not customary in a sanitary 
examination to make a detailed study of all the different forms found 
in a water because of the time required, but if it is desirable for future 
study to separate any species that appear on the gelatin plates, it can 
best be done at this time. 

139. Direct Physiological Tests. —The labor and time involved in 
the separation of the various forms of bacteria in any water are such that 
it is generally preferable to make direct tests with the water itself. 
This method rests upon the principle that when a mixture of different 
forms is placed in any special environment, one or at most a few species 
will thrive more luxuriantly than others. The species so gaining the 
ascendency will tend to hold other species in subjection, so that in this 
way, even in liquid-culture media, almost if not quite a pure culture 
can frequently be obtained by incubating a quantity of water under 
special conditions. 

In these physiological tests the analysis is usually directed toward 
the determination of those properties that are more or less characteris¬ 
tic of bacteria associated with sewage. This raises the important 
question as to whether there is a distinctively sewage or fecal class of 
bacteria, a question which in the light of our present knowledge cannot 
be answered in a wholly satisfactory way. 

If different physiological tests are made of dilute sewage or water 
polluted with such organic matter, it will generally be noted that the 
following characteristics are to be observed. 

Besides a relatively large number of bacteria, cultures made in 
fermentation-tubes with glucose broth will show the presence of gas in 
considerable quantities and of fairly constant composition even when 
seeded with small'amounts of water. Plate cultures of lactose agar to 


128 


EXAMINATION OF WATER-SUPPLIES. 


which litmus has been added (Wurtz’s method) which have been 
incubated at blood-heat or slightly above will generally show numerous 
colonies, many of which are acid-producing, and hence turn the medium 
red. Water inoculated in Dunham’s solution or glucose-free broth 
(Smith) and tested for the presence of indol may be expected to give 
a positive reaction. 

These characteristics are so constant an accompaniment of sewage 
pollution that positive findings as above with a water inoculated directly 
is evidence sufficiently strong to warrant a more comprehensive study 
as to the exact character of the bacteria in the water. A water that 
shows none of these physiological characters is one that is above sus¬ 
picion. On the other hand, a water that reacts positively to these 
tests may be polluted with sewage, or it may be that the bacteria pro¬ 
ducing these characteristics have come from some other source. 

It must be said that these physiological characters are not confined 
to organisms of a fecal origin. Often they are found with forms that 
are associated with the decomposition of organic matter and hence may 
be present in the upper soil-layers. 

It is evident, therefore, that a surface-water might contain organ¬ 
isms that would respond to these tests and yet not be contaminated 
with sewage; but if such characteristics were prevalent in water taken 
from a deep well, they would have more significance. 

140. Value of Qualitative Tests in Comparing Waters. —Reference 
has already been made to the value of quantitative determinations 
(bacterial or chemical) in comparing waters to determine effect of 
leakage, pollution, etc. Not infrequently these physiological tests may 
throw light on cases where quantitative data do not suffice, as in the 
experience of one of the authors where this method was success¬ 
fully used in determining the presence of a leak in an intake-pipe that 
was carried across a somewhat polluted bay. The supply was from a 
ground-water, and a determination of fermentative tests of the water 
taken directly from the wells in comparison with that at the pumping- 
station showed the predominance of gas-producing species in the water 
after having crossed the bay. Quantitatively the difference in bacteria 
was masked by the presence of Crenothrix in considerable amounts, 
which made it difficult to secure comparative samples. 

141. Anaerobic Cultures. —The ordinary bacterial methods are those 
which permit of the growth of forms able to thrive in atmospheric air. 
There are a comparatively large number that possess the propertv of 
growing quite as readily in an atmosphere devoid of free oxygen, and 
also a smaller group that are unable to grow in ordinary air but require 


BACTERIAL EXAMINATION OF WATER. 


129 


some other gaseous environment. Such bacteria are known as 
anaerobes (forms living without air). Those obliged to forego atmos¬ 
pheric air are obligate anaerobes; those able to live under either condi¬ 
tion are facultative or optional anaerobes. 

In soil rich in organic matter, whether from man or animals, and 
therefore in sewage, these anaerobic lorms are frequently found. 
Hence it is often customary to include anaerobic cultures in a bacterio¬ 
logical examination of a water. Bacillus enteritidis sporogenes , regarded 
by Klein as diagnostic of sewage, is a pathogenic organism of this class. 
The technique required in these cultures differs materially from other 
methods, for the atmospheric air must be replaced by some indifferent 
gas or at least the oxygen absorbed. 

142s, Animal Tests. —Some investigators * follow the practice of 
inoculating directly into animals a beef-broth culture made by adding 
water direct. Varying quantities of water are incubated in beef bouillon 
or a peptone solution, and such animals as white mice, white rats, 
guinea-pigs, doves, or rabbits are inoculated with varying quantities of 
the culture. The animal may be killed by the toxic products formed 
in the culture, or it may die from direct infection. This can be readily 
determined by making subcultures from such organs as the liver, 
spleen, or kidney. It does not necessarily follow that organisms 
capable of killing lower animals are able to cause disease in the human, 
but the presence of such forms is certainly undesirable in water, and 
supplies containing such are generally regarded as polluted. 

143. Concentration of Organisms in Water. —Where the degree ot 
pollution is very slight, it oftentimes becomes very difficult to determine 
the presence of dangerous bacteria. It must be kept in mind that 
water suitable for human use is not generally adapted to the growth 
of specific pathogenic bacteria (222); consequently such organisms 
may be present in such sparse numbers as to elude detection. Then, 
too, the amount of water that is ordinarily subjected to a bacteriological 
test is so small as to render it difficult to determine the presence of 
occasional forms. 

Filtration. —When necessary the germ content of a water can be 
concentrated by filtering a relatively large quantity through a germ- 
proof filter (Pasteur or Berkefeld system). Cultures can then be made 
of the sediment adhering to the filter. 

Enrichment Cultures. —Another method is to incubate the water 

sample under such conditions as to composition of culture medium, 

. -«-—---•-■— ■ - - 

* Vaughan, Arch. f. Hyg., xxxvi. p. 190; Blachstein, Ann. Fast., 1893, vil. p- 
689. 





130 


EXAMINATION OF WATER-SUPPLIES . 


temperature, etc., as to cause certain types of organisms to grow 
luxuriantly while possibly holding back other forms not desired. With 
some bacteria that are of importance in water analysis (B . coli, Sp. 
cholerce Asiatica), these enrichment methods are successfully used; 
but unfortunately with the typhoid organism no method has yet been 
devised that can be employed in a thoroughly satisfactory manner 
(148). 

It is evident that the presence of distinctively pathogenic bacteria 
is sufficient to condemn any supply for potable purposes, but the brief 
existence of these forms in drinking-waters makes it difficult to use 
such a standard for the practical determination of the quality of water- 
supplies. While of course it would be desirable to be able to isolate 
such from suspected waters, yet direct proof of their presence *is not 
necessary to justify a condemnation of a supply. If a water shows 
unmistakable evidences of sewage pollution, this in itself is sufficient 
proof to warrant the same being considered dangerous. If this fact is 
associated with an increase in typhoid cases especially, the proof is 
practically as strong as if the typhoid germ itself were found therein. 
It therefore follows that if there is a distinctively sewage class of 
bacteria that can be readily determined, it is of the greatest import¬ 
ance to recognize the same. 

144. Significance of Certain Bacteria in Waters. —An examination 
of the intestinal contents of man and animals shows at least one species, 
B. coli communis, that is so constantly present that it is generally 
known as the fecal bacillus. B. subtilis , the common hay bacillus, is 
very frequently found in animal discharges. Proteus forms are usually 
associated with proteid decomposition. B. lactis derogates , a gas-pro¬ 
ducing species allied to the colon germ ( B . coli comm .) is a common 
form in the evacuations of infants and young children. B. cloacce has 
been regarded as diagnostic of sewage, but this is denied by Theo. 
Smith, who finds it a frequent accompaniment of organic decay. The 
anaerobic organism, B. enteriditis sporogenes , is generally found in 
sewage, although less frequently than B. coli. This germ according 
to Klein * is able to produce diarrhceic disturbances. It can be detected 
where one part of sewage has been added to 500,000 of water. 

145. B. Coli as an Index of Sewage Pollution. —The majority of 
these forms, however, are not distinctively sewage species, although 
they may often appear in such material. More importance in this 
regard has been attached to the colon germ because of its constant 
presence in human feces, and also because it simulates closely the 


* English Loc. Govt. Bd. Rept., 1897-8; Med. Supp., p. 212. 






BACTERIAL EXAMINATION OF WATER. 131 

typhoid-fever germ in some of its culture characteristics. Still the 
most that can be said is that its detection in a water indicates a strong 
possibility of pollution with fecal discharges without proving it. It is 
true that it may have originated from animal sources, indeed possibly 
from the excreta of fish, but the probable origin of the organism will 
be largely determined by the character of the local surroundings, which 
must always in any event receive due weight in any examination. 
Some writers have attached more significance to the number present 
in any given quantity of water. Where found in abundance it has been 
regarded as indicating more undesirable conditions than where it occurs 
sporadically. 

Not infrequently its presence has been reported under conditions 
that make it difficult to explain its origin. Rosenau * in San Francisco 
found it in wells sunk from 130-180 feet in the gravel; von Freudem 
reich t has noted it also in deep springs. 

There exists a close affinity between the typhoid and the colou 
germs as determined by the size, form, motility, and general culture 
characters. When different cultures of these two species taken from 
various sources are studied comparatively, it is found that the cultural 
and physiological characters of both germs are subject to considerable 
modification. Both vary from the type. This condition has 
undoubtedly led to much confusion in the past, and has been held by 
some to substantiate the view that B. typhosus and B. coli communis 
are merely varieties of the same germ,—that B. typhosiis is a form that 
has acquired more pronounced pathogenic powers, although originally 
it was derived from the more common fecal type.J This view is not 
shared by the majority of observers, and while most admit the tenden¬ 
cies of both organisms to vary, but more particularly the colon germ, 
they consider them distinct enough to warrant separation. 

146. Isolation of B. coli. —The relative importance of this microbe 
as indicating the previous history of a water, and the close relation it 
bears to the disease germ of typhoid fever, invests its isolation from 
waters with more than ordinary interest. For this purpose a variety 
of methods have been suggested, some of which are of approximately 
equal value. The more satisfactory of these employ the same principle 
as is applied to the incubation of water direct, i.e., to encourage the 
more rapid growth of B. coli , by placing sample under especially 
favorable conditions for the growth of this and allied species, while 

* Hill, Public Water-supplies, p. 28. 

f Cent. f. Bakt ., 1895, xvm. p. 102. 

\ Villinger, Arch. f. Hyg ., xxi. p. 101. 




132 


EXAMINATION OF WATER-SUPPLIES. 


checking as much as possible the development of the normal indigenous 
water flora. For this purpose it is of service to incubate at high 
temperatures, 98-100° F., in litmus lactose media, in glucose broth 
in fermentation-tube, or in media to which certain antiseptics have 
been added. 

147. Detection of Specific Disease Bacteria. —Not infrequently are 

B. coli and the Proteus species found in pathological processes in the 
human body, but nevertheless these species are not usually regarded 
as pathogenic. Typhoid fever, cholera, and dysentery are the dis¬ 
tinctively water-transmitted diseases. It might with propriety be 
thought that the bacterial method would permit of their ready detec¬ 
tion, but as a matter of fact it does not. There are several reasons 
why this is so. 

1 . These pathogenic microbes do not find in drinking-water a 
favorable environment. They may live in such a medium for some 
time (222), but it is questionable whether under ordinary conditions 
actual multiplication of cells takes place unless there is a degree of 
pollution due to influx of organic matter that practically makes a cul¬ 
ture medium of the water (193). 

2. Owing to the considerable period of incubation (9-14 days in 
the case of typhoid) that must elapse between time of infection and 
appearance of outbreak before waters would ordinarily be subjected to 
examination, it is quite probable that the disease germ may frequently 
have disappeared. 

3. Difficulty of detection is increased because ordinarily the amount 
of water submitted to examination is only a few centimeters at most, un¬ 
less the concentration of bacterial life by filtration is resorted to (143). 

4. Inability, especially in the case of typhoid, to find an elective 
medium that will permit of the rapid growth of this germ, while at the 
same time retarding the development of B. coli or other luxuriant con¬ 
geners. 

These reasons suffice to show some of the difficulties that the 
analyst has to contend with in this phase of his work, yet, in spite of 
these unfavorable conditions, the presence of such disease organisms 
as cholera and typhoid have been determined in a considerable number 
of cases. It should be said, however, that in these cases the conditions 
were rendered especially favorable through the timely search and 
facilities for such examinations. 

The methods that are the most successful in the isolation of specific 
organisms are those which permit of a preliminary development of the 
water sample under conditions extremely favorable for the growth or 


BACTERIAL EXAMINATION OF WATER. 


133 


the species for which search is made. The use of elective media there¬ 
fore necessitates the introduction of different methods in each case, for, 
as a matter of fact, the biological requirements ol the different patho¬ 
genic bacteria are rarely similar. 

148. Isolation of Typhoid Organism. —Although an enormous amount 
of labor has been spent in attempting to find an elective medium that 
would favor the rapid development of the typhoid bacillus in contradis¬ 
tinction to its closely related associate, the colon organism, the results 
are not yet wholly satisfactory. Many methods that have given quite 
satisfactory differential data on a few cultures have failed when tested 
on cultures of diverse origins. The natural variability of the colon 
organism is such as to make it difficult to secure a method that will 
differentiate all the possible varieties. 

Both the colon and the typhoid organisms show a marked tolerance 
toward acids and certain antiseptic substances, but unfortunately the 
colon bacillus is the more robust of the two, and is therefore generally 
able to grow in a medium in which the typhoid organism will thrive. 
On this account it is impossible with our present knowledge to take 
advantage of a medium that will permit of the rapid development of 
Bacillus typhosus , while at the same time holding Bacillus coli communis 
in subjection. 

There exist, however, several cultural and physiological characters 
that are so nearly characteristic as to be of much service in the final 
identification of the typhoid germ. In contradistinction to B. coli , B. 
typhosus does not ferment sugar solutions of any kind in the fermenta¬ 
tion-tube, neither does it produce indol. It does curdle milk in time, 
although the acid production in comparison with B. coli is much less. 
Since the introduction of the Widal test in diagnosing typhoid fever, 
it has become possible to take advantage of a reaction that is so specific 
as to be of greatest service. If a fresh culture of a genuine typhoid 
organism is brought in contact with the blood of a person suffering from 
this disease, the bacilli lose their motility and become aggregated in 
clumps, a phenomenon known as the Widal reaction, now so exten¬ 
sively used in the diagnosis of this disease in the human. By taking 
advantage of this fact, it is possible to test a doubtful germ against a 
positively known typhoid blood. If the isolated culture gives the 
Widal reaction with known typhoid blood and does not with perfectly 
healthy blood, the evidence as to nature of the organism in question is 
practically decided, for when properly examined the per cent of 
accurate returns from this test is very high, approximating the possible 
limit. 


134 


EXAMINATION OF WATER SUPPLIES. 


149. Isolation of Cholera. —This organism grows with great rapidity 
in alkaline solutions of peptone and salt. By taking advantage of this 
characteristic and incubating suspected samples of water at blood-heat, 
the cholera spirillum can be greatly increased in number so that a 
subsequent examination of the surface pellicle will generally indicate 
the presence of cholera-like organisms. If positive microscopic find¬ 
ings are made by this enrichment method, the preparation of subcultures 
in various media will soon tell positively whether the organism is the 
genuine “comma bacillus ” of cholera or a spirillum of similar form, a 
number of which occur in flowing or surface waters. 

The culture characters of the cholera germ are fairly distinctive, 
but there are two tests that are considered so specific as greatly to aid 
in diagnosis. These are the cholera-red reaction (indol test) and 
Pfeiffer’s phenomenon. Tests of this character can be made only by 
the bacteriological expert. 

150. Disinfection of Polluted Wells and Pipes. —It may happen that 
wells and water systems may sometimes become temporarily polluted 
with disease-producing matter, without such material continuing to find 
its way into the same. Under such circumstances it is necessary to 
disinfect the water system in such a way as thoroughly to destroy all 
disease organisms. These methods should not be interpreted as 
applying to wells that are so poorly constructed that surface-drainage 
cannot be kept out. Such wells should be condemned and closed. 
Open or dug wells are much harder to disinfect thoroughly than tubular 
wells, owing to the larger cubical content, but more particularly to the 
loose and open character of the walls. Driven or drilled wells enclosed 
in iron pipes can be disinfected with little or no difficulty should they 
happen to become infected. 

For this purpose several methods have been used. Neisser found 
that steam could be very successfully employed. A pressure of 50-60 
pounds per square inch succeeded in raising the temperature of a well 
containing about 500 gallons from 50° to 210° F. in 2 \ hours. This 
destroyed all trace of the organisms added, although it did not render 
the well wholly sterile. 

A solution of crude carbolic and sulfuric acid can also be added to 
wells with good results.* In old wells, particularly those that are 
open, dirt collects in the bottom, in which case the bacteria retain 
their vitality for some time. The disappearance of the carbolic acid in 
water can be detected by applying ferric chloride. 


* Frankel, Zeit. f. Hyg., vi. p. 23. 




BACTERIAL EXAMINATION OF WATER. 


135 


Sometimes it becomes necessary to disinfect the whole hydrant 
system. According to Stutzer* 0.05 per cent solution of sulfuric acid 
suffices to destroy the cholera organism in 15 minutes in distilled 
water. As this acid unites readily with the alkaline earths and iron 
present in the water, it is necessary to increase the amount added. 
For actual disinfection work he used 0.2 per cent. The acid solution 
is allowed to fill the entire system, remain in contact with the same a 
number of hours, and is then flushed out. In disinfecting the water- 
mains after the cholera epidemic of Hohenlohehiitte and the typhoid 
outbreak in Freiburg, he found that it took about three days to remove 
all trace of the acid, but the bacterial tests of the water were then 
found to be wholly satisfactory. 

151. Bacterial Control of Filter Operations. —To determine the effi¬ 
ciency of a filter system as a means of purifying water-supplies, the 
bacterial method of examination has evident advantages. This is done 
by making a quantitative bacterial examination of the water before and 
after being applied to the filter. A chemical analysis generally shows 
but little improvement because most of the substances determined are 
of a soluble nature, and therefore readily pass the pores of the filter. 
The real elements of danger in water, however, are the living organ¬ 
isms—the disease bacteria, and these are prevented, by reason of their 
insoluble nature, from passing through a properly constructed filter. 

Of course there is no differentiation in the filter between those 
species capable of producing disease and the harmless water inhabit¬ 
ants, but a determination of the percentage removed from water during 
filtration gives an approximate estimate of the degree of efficiency of 
the filtering process. At first it was throught that an enumeration of 
the number of organisms in the applied water and the effluent would 
give the exact extent of purification, but later it was found that some 
bacteria possess the ability of growing in the body of the filter and 
underdrains, and so the number in the effluent may not represent the 
actual number passing the filter. 

Later the custom was introduced of applying cultures of some 
specific kinds of bacteria not normally found in the filter sand, and 
determining the number of such organisms in the effluent. Bacillus 
prodigiosus, one of the most characteristic pigment-producing bacteria, 
has been used for this purpose to a considerable extent, but of late 
years. B. coli comnnmis f has been more extensively employed because 

* Zeit. f. Hyg.,x\\. p. 116. 

f Clark and Gage, Jour. Bost. Soc. Med. Sc., 1900, iv. p. 172. 




136 


EXAMINATION OF WATER-SUPPLIES. 


of its closer relation to disease bacteria and the fact that it is in a sense 
an index of fecal pollution. 

The importance of a careful examination of filter-works by this 
method is especially recognized in Germany, where every municipality 
using sand-filtered water is obliged to make frequent reports, especially 
on the bacterial results, to the Imperial Board of Health, as to the 
working of the filters. 


MICROSCOPICAL EXAMINATION OF WATER. 

152. Scope of Microscopic Examinations. —In the microscopical 

examination of water a determination of the suspended matter other 
than bacteria is generally included. This may embrace particles of 
inorganic as well as of organic origin. An opalescent water may 
sometimes be caused by extremely fine fragments of clay that may 
even be so small as to pass a filter. Quartz splinters or particles of 
iron oxide also not infrequently occur. These inorganic materials have, 
however, no sanitary significance, but their recognition becomes a 
matter of import only as explaining the physical condition of water. 

Of far more importance is the material of organic origin. Much 
may be learned of the nature of a water and its possible sources of 
pollution by a microscopic examination, which generally permits of a 
differentiation between matters of animal and vegetable character. A 
recognition of any fibers, such as cotton, wool, or flax, starch grains, 
and undigested muscular tissue indicates a source of pollution generally 
due to household wastes. 

In matter of distinctively fecal origin it is possible that eggs of some 
of the intestinal parasites of man and animals may be present. Many 
of these retain their reproductive powers for a long time, but fortunately 
are unable to develop in man directly, requiring an intermediate host 
(201). 

In addition to such microscopic findings as reveal the presence of 
suspended particles that are often closely related to house-refuse, there 
are a large number of living organisms whose natural habitat is that of 
water. These may be either animal or vegetal (183). Generally speak¬ 
ing, their presence in water-supplies is not such as to render the water 
dangerous to human health; * but not infrequently the physical quali¬ 
ties of the water (taste, odor, color) may be profoundly modified by 
their presence. As Whipple well says, bacteria may render a water 
unsafe, but other microscopic organisms are likely to make it unsavory. 


* Neisser, Zeit. f. Hyg. , xxii. p. 475. 




MICROSCOPIC EXAMINATION OF WATER. 


13 7 


A direct microscopical examination will not generally reveal many 
forms unless precautions are taken to concentrate the same in a small 
volume. For this purpose plain sedimentation will not suffice, but a 
method of filtering large quantities of a water through sand has been 
generally adopted (Sedgwick-Rafter method).* 

In many waters organisms of this class occur only sparingly, or 
they possess no disagreeable properties that impair the quality of the 
water; hence their presence is of no particular import. In other cases 
certain species are so abundant that the quality of the water is dis¬ 
tinctly injured by their presence. 

Difficulties of this sort are quite apt to occur in stored waters, as in 
ponds or reservoirs, for the access of light is necessary for the develop¬ 
ment of these plant-forms. Filtered or ground-waters are very prone 
to develop these troubles unless reservoirs are covered. 

153. Direct Microscopic Examination in Filtration-work. — The 
microscopical method of examination is sometimes of service in com¬ 
paring waters, as in the case of sand-filters or in filtration-galleries. 
One of the writers once had an opportunity successfully to use this 
method in determining the presence of a leak in a submerged pipe, 
the outer water being a surface-water and therefore containing algae. 
In determining the efficiency of filtration in filter-galleries, it is 
necessary to use freshly filtered waters, as microscopic organisms are 
likely to develop rapidly in such waters open to the sunlight. In 
Taunton, Mass., trouble was experienced in the water from a filter- 
gallery from the growth of both Asterionella and Dinobryon (183). 

SANITARY SURVEYS. 

154. Object and Value. —The normal condition of the water-supply 
of different regions is subject to considerable variation. Even that of 
the ground-water, which is generally supposed to be more stable, fluc¬ 
tuates in different parts of the country with reference to many of its 
constituents. In some cases local causes are operative in changing the 
nature of the supply, as in the case of hard waters in limestone regions. 
The same holds true with reference to the proximity of the sea, the 
chlorine content gradually diminishing as the distance from the sea 
increases (123). 

In different States these sanitary water-surveys are being taken up 
by the respective Health Boards, and the normal condition of the 
water-supplies determined. These afford a basis for comparison that 

* For details of apparatus and use, see Whipple’s Microscopy of Drinking-water, 

P. 15 - 





EXAMINATION OF WATER-SUPPLIES . 




133 


enables the analyst to judge more accurately as to whether any water 
he is testing is abnormal or not for the region from which the sample 
comes. 

Not only are these sanitary surveys being made of the ground- 
~water supplies, but the surface-waters are now receiving considerable 
attention. The importance of this is readily recognized when one 
considers that the supplies for our larger municipalities must of necessity 
be drawn from open waters, as these are often the only adequate 
sources that can be used. With the steady growth in our urban popu¬ 
lations and the consequent increased danger of pollution, it becomes 
more and more necessary to secure these supplies from distant sources 
that are free from pollution, or to purify those that are more available 
and more likely to be polluted. 

To keep close check on the effect that the constant increase in 
population has, it is necessary to know the normal conditions of a 
water-supply, both chemically and bacteriologically. If these surveys 
are made before the sources are polluted, then a standard of compari¬ 
son can be had from which the effect of a growing population can be 
determined. For instance, the Massachusetts and the English sanitary 
authorities estimate that the increase in chlorine content is between 
.4 and .5 part per million for an increase of every 100 persons per 
square mile. 

The absolute necessity of thus determining the quality of waters 
that are to serve as sources of supply for large cities is evident, but 
these sanitary surveys are now being extended so as to include entire 
river systems. The Ohio State Board of Health is now engaged in a 
study of the character of the surface-waters of the State. A similar 
survey of the Illinois River is now being made by the city of Chicago 
to ascertain the present normal condition of this river and so determine 
just what change the drainage canal of Chicago will have on the quality 
of the water of that stream. Cities situated on large streams very 
often use these as natural drainage-channels for sewage disposal. The 
'Consequence is that the pollution in such streams is constantly increas¬ 
ing, so that municipalities situated farther down-stream are in danger 
of having their most available source of water-supply polluted from the 
wastes of other towns. It is true that there is a natural purification 
process (168) going on in such rivers, but the question is always per¬ 
tinent as to whether such natural processes are wholly able to purify 
the water. To obtain a basis from which to determine whether con¬ 
ditions are materially changed as density of population increases, these 
sanitary surveys are of great value. 


LI TER A TURK. 


J 39 


LITERATURE. 

For a more detailed consideration of different phases of sanitary analysis, 
reference may be made to the following list. This list is not intended to be 
exhaustive, but merely comprehensive enough to direct the sanitary engineer 
to the more important publications relating to the sanitary analysis of water, 
and the interpretation of such work. The technical water analyst will need to 
consult much of the chemical and bacteriological periodical literature in order 
to learn of methods available for his work. 

Questions of technique are considered more or less in detail in all of the 
following books : 

P. & G. C. Frankland. Micro-organisms in Water. 1894. 

A resume of the bacteriological phase of the subject, including 
a description of over 200 species of bacteria found in waters. 
Tiemann-Gaertner. Handbuch d. Untersuchung u. Beurtheilung d. Wasser r 
Vierte Auflage. 1895. 

A complete handbook on matters relating to both chemical and 
bacteriological examination of water-supplies. 

Loeffler, Oesten and Sendtner, Wasserversorgung, Wasseruntersuchung u. 

Wasserbeurtheilung. 1896. (In Weyl’s Handbuch der Hygiene.) 

Very useful to the engineer as well as the water analyst. 
Leffmann and Beam. Examination of Water for Sanitary and Technical Pur¬ 
poses. 1895. 

Confined to the chemistry of the subject. 

Pearmain and Moor. Chemical and Biological Analysis of Water. 1899. 
Mason. Examination of Water. 1899. 

A revised reprint of two chapters on chemical and bacteriological 
examination of water included in his larger, more general work on 
Water-supply which appeared in 1896. 

Miquel, P. Manuel pratique d’Analyse bacteriologique des Eaux. 1891. 
Roux, G. Precis d’Analyse microbiologique d’Eaux. 1892. 

Fuller, G. W. Water Purification at Louisville. 1898; also,—Report on 
Water Filtration at Cincinnati. 1899. 

While primarily concerned with filtration experiments, yet valu¬ 
able for full exposition of analytical methods. 

Hill, John W. Public Water-supplies, 1898. Although written from the general 
engineering point of view, this work contains valuable data that will be 
of use not only to the general student but the technical analyst as well. 
Williston, Smith, Lee, and Foote. Rept. on Exam, of Conn. Water-supplies. 

14 Rept. Conn. Bd. Health, 1891, p. 231. 

Whipple. The Microscopy of Drinking-water. 1899. 

A most complete presentation of the relation of microscopic 
organisms other than the bacteria to water-supplies, including a 
classification of such organisms as far as genera. An indispensable 
book to the student of this phase of water investigation. 

The Bibliography of analytical methods of water analysis is quite volumi¬ 
nous, and widely scattered in numerous scientific journals, as well as more tech¬ 
nical publications. Besides the references already given as foot-notes to the 
text, the reader is referred to the following list of papers that include those 
of general interest, as well as some that relate mo r e specifically to the 
technique of water examinatiop : 


140 


EXAMINATION FOR WATER-SUPPLIES. 


Plagge and Proskauer. Die hygienische Beurtheilung d. Wassers auf Grund 
der Ergebnisse d. chemische u. bact. Untersuchung. Anhang zu 
Bericht u. d. Unters. d. Berliner Leitungswasser, Zeit. f. Hyg., 
1887, 11. p. 470. 

Hueppe, F. Die hyg. Beurtheilung d. Trinkwassers v. biol. Standpunkte. 

Schilling’s Journ. f. Gasbeleuchtung u. Wasserversorgung, 1887. 
Kruse, W. Kritische u. experimentelle Beitraege z. hygien. Beurtheilung d. 

Wassers. Zeit. f. Hyg., 1894, xvn. p. 1. 

Frankland, Percy. The Hygienic Value of the Bacteriological Examination 
of Water. Trans. 7th Internal. Cong, of Hygiene and Dernog. 
London, 1891. 

Drown, Thos. M. The Interpretation of Water Analyses. 24 Rept. Mass. 
Bd. Health, 1892, p. 319. 

The Chemical Examination of Waters and the Interpretation of Analyses. 

Examination of Water-supplies, Part I, Mass. Bd. Health, 1890, 
p. 519; also 24 Rept. Mass. Bd. Health, p. 533. 

Jackson, D. D. Improved Filter for Microscopic Water Analysis. Technology 
Quarterly, 1898, xi. p. 241. 

Fuller, G. W., and W. R. Copeland. Quantitative Determination of Bacteria 
in Sewage and. Water. Mass. Board of Health Report, 1895. 
Convention of Bacteriologists, June, 1895, held under auspices of Com. on 
Pollution of Water-supplies of the American Pub. Health Assn. 
Journal of the American Public Health Assn., 1895. 

Procedures recommended for the Study of Bacteria. Rept. Com. of Amer. 

Bacteriologists to the Com. on Pollution of Water-supplies of the 
American Public Health Assn. Journal of the American Public 
Health Assn., 1898. 

Sanitary Surveys. Sanitary surveys of individual streams, watersheds 
furnishing municipal supplies, and in some cases general state surveys have 
been or are being made, generally under public auspices. In some cases these 
surveys have been undertaken from the chemical point of view; in other 
instances both chemical and bacteriological examinations have been made. 

The most extensive work yet performed is that done under the auspices of 
the Massachusetts State Board of Health. (See Report on Exam, of Water- 
supplies, 1890 c/^y.) 

Similar examinations have also been made in Connecticut (18 Rept. Conn. 
Bd. Health, 1895, p. 230). 

In New York a careful sanitary survey has been made of the Croton water¬ 
shed, the base of supply for New York City (9 Rept. N. Y. State Bd. Health, 
1889, p. 189); also a chemical and bacteriological study of the Mohawk- 
Hudson valleys (12 and 13 Rept. N. Y. State Bd. Health). 

Similar surveys were begun by the Ohio Bd. of Health in 1897. Two 
reports have already been issued (1897 and 1900), embracing the results 
obtained in the study of five of the larger river systems of the State. 

In the State of Illinois the State Board of Health is making a chemical sur¬ 
vey of the water-supplies. (Report published 1897. ) 

At present there is also being made a complete sanitary study of the Illinois 
River in connection with the Chicago Sanitary Drainage Canal. This work is 
being done independently by the cities of Chicago and St. Louis, but no 
reports have yet been published. 


' 1 



CHAPTER IX. 

QUALITY OF WATER. 

155. Importance of Quality. —In securing a water-supply for public 
or for private use, the question of quality is of supreme importance. 
An adequate or copious supply is not so much to be desired if it means 
that quantity must be purchased at the expense of quality. In this 
respect European cities are much ahead of American municipalities. 
The per capita consumption in this country is greatly in excess of that 
of Europe, but in the matter of quality they frequently excel our 
standards. 

Pure water from the standpoint of the chemist is not to be found 
in nature; neither is it desirable that such should be furnished for 
general purposes, for the presence. of certain salts in water makes it 
more palatable and better for use than distilled water. The origin of 
all water-supplies is primarily to be traced to the rainfall, although it 
by no means follows that the supply utilized in any particular region is 
derived from the precipitation in that immediate locality. 

As has previously been shown, the rainfall is either evaporated from 
the surface of the earth, funs off, or percolates into the ground. Only 
that which remains on the surface or in the soil is of any avail as a 
source for water-supplies. Between the surface “run-off” and that 
which flows beneath the surface there is a constant interchange which 
exerts its effect on the quality of the water. 

156. Changes in Quality Determined by Course of Water. —As it 
condenses in the atmosphere and falls to the earth’s surface, it begins 
to absorb impurities; and its whole history from the time it is precipi¬ 
tated until it finally finds its way back into the air through evaporation 
is marked by the absorption of substances which pass into solution or 
are held in suspension, as well as the precipitation or elimination of 
the same or other ingredients. Some of these changes are harmless 

so far as affecting the ordinary use to which water is put; others are of 

141 


142 


QUALITY OF WATER. 


much consequence, depending upon the requirements to which the 
water-supply is subjected. 

157. Requirements as to Quality.—The ordinary purposes to which 
water-supplies for human use are put may be included under the fol¬ 
lowing heads: potable, domestic, and manufacturing uses. So far as 
quality is concerned, the conditions desired for each purpose do not 
necessarily coincide. 

158. Potableness.—A suitable supply for drinking purposes should 
not only be pleasant and palatable, but if possible free from any 
marked color or turbidity. While these latter requirements are desir¬ 
able, they are not obligatory, for experience has fuHy demonstrated 
that many peaty supplies and often turbid waters may be used with 
perfect safety. A potable water should not be excessively charged 
with mineral matter in solution. Mineral waters have a value for 
medicinal purposes, but not as general supplies. It has long been a 
disputed question as to the effect on human health of waters heavily 
loaded with dissolved mineral matter. A common prejudice exists 
against the use of very hard waters, as they are supposed to result in 
the production of various diseases, as urinary calculi, goitre, cretinism, 
etc., but there are no established scientific data that would positively 
confirm such an opinion. It is more likely that intestinal and gastric 
disturbances may occur where permanently hard waters are used. 

It sometimes happens that water may dissolve poisonous metals 
either in the soil, or in pipes used for distributing purposes, and so 
become unwholesome. Lead, zinc, and iron are the metals most 
likely to occur under such circumstances. Where water is acid, as in 
peaty waters, or where C 0 2 is present in large quantities, the solvent 
action on the lead is much increased. In such .districts many cases of 
lead poisoning not infrequently occur, although all waters of this class 
are not necessarily affected. Zinc is much less liable to cause trouble, 
although where water is in contact with galvanized pipes an appreci¬ 
able amount of zinc may often be determined. When iron is present 
in waters it generally comes from the source of supply, and is not 
derived from the pipes except under certain circumstances. Where 
present in the proportion of O.5-1.O part per million, the water gener¬ 
ally has an objectionable taste, and while the presence of this metal in 
small quantities is not attended with serious results on health, its unde¬ 
sirable taste and appearance is against its use. 

The danger of direct absorption of poisons from water is, however, 
small compared with that attributable to the influence of disease organ¬ 
isms. Typhoid fever and other diseases of an intestinal character not 


GENERAL QUALITIES OF WATER . 


143 


infrequently find their way into water-supplies, often causing widespread 
epidemics of these infectious maladies; but this subject is of such im¬ 
portance as to require more detailed treatment later (Chapter X). 

159. Domestic Use. —For ordinary domestic use the quality of water 
must be such that it can be used in cooking and for laundry use. For 
these purposes water should not contain too large a proportion of 
mineral ingredients. Naturally, the same sanitary requirements that 
are necessary in drinking-water also obtain in water used for culinary 
purposes. Excessively hard waters are not desirable, as the flavor of 
many foods is considerably impaired when cooked in the same. Iron¬ 
bearing waters are also unsuitable for this purpose, as the tannin in tea 
and many vegetables produces a black precipitate. These waters are 
likewise detrimental for laundry use, as the oxidation of the ferrous salts 
upon exposure to the air produces rust-spots upon clothes. The greatest 
difficulty to contend with in the laundry in the case of ground-waters 
is the presence of soluble salts of alkaline earths, such as lime and 
magnesia. When soaps are added to such “hard ” waters, insoluble 
precipitates are produced, and it is therefore necessary to use a much 
larger quantity of soap before a lather can be produced. One part of 
lime carbonate requires about eight of soap, so the problem from an 
economic standpoint is one of importance. It is estimated that the 
city of Glasgow saves $180,000 annually in the amount of soap used 
since the introduction of the soft Loch Katrine water.* 

The hardness of water is either temporary or permanent, depending 
upon the chemical nature of the dissolved salts. If bicarbonates are 
present, the CO., contained in the same is set free by boiling, in which 
case a white precipitate consisting of carbonate of lime is formed. As 
this reduces the amount of lime in solution, the hardness is diminished, 
and such is’therefore called temporary, in contradistinction to the 
sulfates and chlorides of lime and salts of magnesia that are not so 
affected; hence waters containing these salts in abundance are per¬ 
manently hard. 

160. Manufacturing Purposes. —For different manufacturing pur¬ 
poses, such as brewing, sugar-making, dyeing, etc., the quality of 
water is subject to considerable variation. In the production of steam, 
trouble is experienced with all waters containing an excess of salts of 
the alkaline earths by the formation of boiler-scale. With the tem¬ 
porarily hard waters a friable deposit is produced, while permanently 
hard waters cause a much more compact “ scale,” that is very difficult 


* Parkes, Hygiene and Public Health, p. 10. 





144 


QUALITY OF WATER. 


% 


to remove. The accumulation of even a thin layer of boiler incrusta¬ 
tion involves a very marked loss of energy in the coal used. 

161. Distribution of Bacteria in Soil.—To understand aright the 
quality of waters as affected by germ-life in the same, it is necessary 
to know the distribution of bacteria in the soil. Generally the rock- 
masses are covered with a layer of more or less finely ground material 
that makes up the soil. This layer is differentiated into two strata: 
the upper one, the soil proper, that is darker in color and of a more 
porous texture; the lower, known as the subsoil, that simply represents 
the unchanged rock debris. As the soil supports abundant vegetable 
and animal life which, as it dies, is resolved into decomposing organic 
matter, the upper layer becomes enriched through the accumulation of 
the same which serves as future plant-food. The organized tissues are 
first disintegrated by the action of the saprophytic bacteria, as noted in 
the changes of putrefaction and decay. In this process humus is 
formed and the looser texture and darker color of the upper soil-layer 
are attributable to this series of changes. As these processes are con¬ 
trolled by bacteria, it is not surprising to find that the uppermost soil- 
layers are teeming with myriads of these forms, often millions of them 
being present in every gram. This number, however, diminishes 
rapidly below the surface, and at the depth of two or three yards soils 
are practically sterile. Cultivated, but more particularly inhabited 
soils, have a higher bacterial content than virgin forests or prairie soils. 
The character and texture of the soil-layers also influence to some 
extent the distribution of these micro-organisms. The reasons for this 
peculiar distribution lie in the filtering power of the soil-particles as the 
moisture percolates downward; in the absence of organic food-supplies 
in the deeper layers; and to generally unfavorable growth conditions 
(lower temperature, diminished oxygen). 

Not only does the soil harbor all kinds of bacteria associated with 
the breaking down of organic matter, but the formation of nitrates from 
the ammonia so produced, due to the nitrifying bacteria, also occurs in 
the upper layers of the soil. 

It is at once evident that the germ content of any water that comes 
in contact with the soil must be profoundly affected by the soil-layers. 
So, too, with the air; for in a dried condition, the fine dust-like particles 
with their adherent organisms are readily raised by wind-currents from 
the surface. Of course by far the majority of these organisms are harm¬ 
less saprophytes; but if disease matter is deposited upon the surface of 
the soil, there is often nothing to prevent the distribution of pathogenic 
bacteria in quite the same way. 


METEORIC WATERS. 


145 


While the germ content of water may be greatly influenced by that 
of the soil, it must be remembered that the flora of the two habitats 
are not necessarily similar. There are to be found in water certain 
species that are so universally present that they may be called water 
bacteria. In this medium they are able to grow with the greatest ease, 
even in waters that are relatively poor in inorganic as well as organic 
nourishment. 


METEORIC WATERS. 

162. Absorption of Impurities from Air. —Meteoric waters include 
the various forms of rainfall, as rain, snow, hail, dew, etc. ; and while 
they are not normally to be considered as immediate or direct sources 
of supply, except occasionally for individual use, yet the fact that they 
serve as indirect sources from which supplies are subsequently drawn 
make it desirable to consider their quality. As watery vapor con¬ 
denses in the air and is precipitated, whether in the form of rain or 
snow, it absorbs impurities from the atmosphere. Particles of dust and 
dirt are washed out of the same, and in the neighborhood of large 
towns, soot and other combustion products may pollute these waters 
to a very considerable degree. The gases that are naturally present 
in the air are also more or less readily absorbed by water. Not only is 
this true with the more important constituents, N, O, and CO.,, but 
such substances as ammonia, sulfuric acid, nitrous and nitric acids are 
generally found. Naturally meteoric waters are deficient in mineral 
matter and hence are soft. Where extremely soft their action on lead 
pipes is severe. 

Water in falling to the ground in the form of either rain or snow 
also takes up germ-life from the air. Bacteria and spores of fungi find 
their way into it in considerable numbers from the subjacent soil-layers, 
and while they are incapable of multiplication in the air, yet in a dried 
condition many forms can retain their vitality for long periods of time. 
The result is that either rain or snow catches these floating forms of 
life and so they are carried down. Even in hailstones they are to be 
found without exception. 

Hill * records some observations made on the germ content of the 
air at different periods during a rain-storm. At first it was very high, 
5495-5759 bacteria per c.c., but after a rain of 12 hours there were only 
15-57 germs. The number of organisms in the air decreases rapidly 
with an increase in altitude. On mountain-sides this is not so marked 
until the snow-line is reached. 


* Public Water-supplies, p. 51. 





146 


QUALITY OF WATER. 


SURFACE-WATERS. 

163. Character Determined by Nature of Underlying Soil. — As 

meteoric waters fall to the earth, a portion of same is evaporated into 
the*air, while the remainder, following the contour of the surface, either 
runs off or percolates into the underlying soil. That which is apparent 
on the surface of the soil is included under the term surface-waters, 
although an appreciable part of such supplies has been subject to more 
or less percolation through soil layers (springs, ground-water drainage 
into rivers). Owing to the fact that surface-waters may be brought 
into contact with mineral and organic matter that renders them more 
or less impure, the quality of such waters is subject to much fluctuation. 
When first precipitated, the character of the water is to a large extent 
determined by the nature of the soil over which it flows and the vege¬ 
table covering of the soil, but in river systems that traverse a wide 
range of territory, the suspended and dissolved impurities are not 
necessarily related to the character of the land drained. 

164. Surface-waters as Potable Supplies. —As organic refuse, either 
of human, animal, or vegetable origin, is generally found on the surface 
of soil, it is evident that the quality of surface-waters is often impaired 
by reason of pollution with such material. Inasmuch as the most 
dangerous refuse of this character is that connected with human exist¬ 
ence, it follows, where pollution is at all possible, that the density of 
population will exercise a potent influence on the character of such 
♦supplies. For this reason the use of surface-waters, particularly those 
of flowing streams in densely populated watersheds, is a menace to pub¬ 
lic health, unless they are first subjected to some adequate method of 
artificial purification. In this respect lake-waters, particularly such 
enormous reservoirs as our Great Lakes, are naturally of much better 
quality than running waters that carry off the surface-wash and drainage 
of large land-areas. This is confirmed by the typhoid death-rates of 
cities using this water in comparison with those furnished with river 
supplies. In 1890-96 the typhoid deaths for the five largest cities 
situated on the Great Lakes averaged 42 per 100,000, while for the 
five largest river cities of the United States it was 58 per 100,000. 

A. Flowing Waters. 

165. Naturally the availability of running streams as sources of 
municipal water-supply has led to their more frequent adoption than 
any other kind of surface-water, but it must be remembered that this is 
not because they are of better quality. Water in flowing over the sur- 


SURFA CE- WA TERS. 


147 

face of the soil naturally acquires numerous impurities that it would not 
take up if it remained quiescent. These substances are of inorganic 
and organic origin, each class being represented by suspended as well 
as dissolved material. One character of flowing waters is the sudden 
change in composition that is liable to occur at almost any time, but 
more particularly during flood seasons. By reason of this, a supply 
that is generally satisfactory may be rendered undesirable in a short 
space of time. Again, not only are running streams the natural drain¬ 
age-channels of a region, but they must to a large extent also serve as 
sewage-outlets for urban populations that are generally increasing in 
density. 

166. Physical Appearance.—Owing to the fact that running waters 
frequently have a considerable fall per mile, thereby producing more 
or less rapid currents, it naturally follows that waters of this class in 
direct contact with the soil erode their drainage-basins with consider¬ 
able rapidity and so become more or less turbid. 

Babb * has compiled the observations made on various rivers as to 
the visible load of sediment. They are as follows: 

Amount of Sediment by Weight. 


Potomac. 1 : 3575 

Mississippi. 1 : 1500 

Rio Grande. 1 : 291 

Danube. 1 : 2880 

Nile. 1 : 2050 


Not only the amount but the nature of this silt varies much in 
different streams, depending mainly on the character of the soil and 
the rate of flow. Some streams, like the Missouri, may possess a very 
turbid water, but the size of suspended particles is such that much of 
this sediment is deposited when the water is quiescent; other streams, 
like the Mississippi and Ohio, carry a smaller load of silt, but the fine 
colloidal clay that is so abundant in the same makes it exceedingly 
difficult to clarify. 

Surface-waters flowing through swampy regions are usually colored, 
due mainly to the extraction of soluble coloring matter from vegetable 
material. Such peaty waters, while perhaps unsightly in appearance, 
may be, however, perfectly wholesome in spite of this physical defect. 

While flowing surface-waters do not dissolve so much mineral 
matter as ground-waters, yet by virtue of their dissolved carbon dioxide 
they also take up an appreciable amount, depending considerably on 
the character of the soil stratum over which they pass. The average 


* Babb, Science , 1893, xxi. p. 343. 









148 


QUALITY OF WATER . 


of a large number of European and American rivers shows about 180 
parts per million of soluble solids, of which nearly one-half is carbonate 
of lime.* * * § 

167. Bacterial Condition of Flowing Streams.—Naturally the close 
contact with the upper soil-layers, which are so rich in micro-organisms, 
accounts for the much higher germ content of rivers and streams than 
lakes. It might be thought that such streams would show a larger 
number of bacteria duing a low stage of water than otherwise, for if the ^ 
sources of pollution were at all uniform, the lessened summer flow would 
tend to concentrate the impurities. As a fact, however, the bacterial 
pollution of a stream is always greater during high-water stages. The 
more rapid rate of flow increases the carrying power of the stream, and 
much more suspended matter, as silt and dirt, is borne along together 
with the bacteria that invariably accompany such disturbance of the 
soil particles. Theobald Smith t found that the Potomac River water 
contained the following number of bacteria at different seasons : 

Dec. Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. 

967 3774 2536 I2IO 1521 1064 348 255 254 178 75 116 

The same general result has been noted by Fuller J in his studies 
on the Ohio River at Cincinnati and Louisville, and by Franklandg in 
the case of the Thames and Lea, two rivers from which London 
derives in part its water-supply. 

According to Johnston || the bacterial content of uninhabited streams 
like the Saguenay in Canada is not materially different from that of 
rivers flowing through farming regions, although where a stream flows 
through a city or town of any considerable size, especially if it receives 
the sewage of the same, the amount of pollution is naturally much 
increased. Prausnitz^T determined the following data for the Isar River 
at Munich. 

TABLE NO. 23 . 

BACTERIAL CONTENT OF ISAR RIVER. 

No. of Bacteria per c.c. 


Above the city of Mimich. 531 

150 feet above sewer outfall. 1,339 

Directly opposite sewer outfall. 121,861 

450 feet below sewer outfall. 33,459 

Ismaning (8 miles below sewer outfall). 9,111 

Freising (20 “ “ “ “ . 2,378 


* I. C. Russell, Rivers of North America, p. 79. 

f Med. News, April 9, 1887. 

% Investigations on Purification of Ohio River, p. 34. 

§ Micro-organisms in Water, p. 91. 

| Hyg. Rnnd. y v. p. 796. 

Tf Der Einfluss d. Munch. Canalisation, 1889. 









SURFA CE- WA TERS. 


149 


Not only is there a marked increase in the bacterial content of the 
river, but it is also evident from the above table that a large part ol 
this pollution is lost in a comparatively short time, as it only takes 
8 hours for the current to reach Freising, 20 miles below. These con¬ 
ditions have since been reinvestigated (1898),* * * § and it has been found 
that over 50 per cent of the bacteria introduced in the sewage are 
eliminated in a flow of twelve miles. 

168. Self-purification of Rivers.—This process of spontaneous puri¬ 
fication is to be noted in all streams that are polluted in any way by 
the introduction of sewage or soil drainage. Not only are organic 
impurities but inorganic as well eliminated in this way. The rate at 
which this process goes on depends upon a number of conditions, such 
as rate of flow, character of bed and shores, amount of sediment carried 
in water, etc. 

Comparative studies (chemical and biological) have been made on 
a number of important streams on which cities are situated. Naturally 
most of the data yet collected are on European waters. 

Stutzer and Knublauch + found an evident purification of the Rhine 
below Cologne in 2 miles’ flow. Six miles below the bacterial content 
on the left shore was reduced to one-third. On the right shore the 
diminution was less rapid, as a tributary brought into the stream a 
large amount of factory waste from other towns. This could be traced 
for a distance of 16 miles below before it disappeared. 

Heider X traced the pollution of the Danube below Vienna for 25 
miles, a distance covered in a flow of 8-9 hours. In this stream the 
sewage of the city was diluted from 225-880 times. Schlatter § in 
1889 observed the effect of the sewage of Zurich for 6 miles, and 
recently Thomann, || in investigating the same problem ten years later 
to determine if the zone of pollution had been materially increased, 
found only one case at the distance of 9 miles where the germ content 
was approximately as low as it was above the city. At this distance 
the average germ content was about 50 per cent higher than before the 
introduction of the sewage. During this period the city had increased 
its population about 50 per cent, so the zone of pollution was propor¬ 
tionally increased. The same result was observed at Munich in study¬ 
ing the Isar, as is indicated in Table No. 24.IT 

* Hyg. Rund., 1S98, vm. p. 161. 

f Cent. f. allg. Gesundheitspflege, 1893, abs. in Hyg. Rund., IV. p. 225. 

% Oest. Sanitatswesen, 1893, No. 31. 

§ Zeit. /. Hyg., IX. p. 56. 

|| Ibid., XXXIII. p. I. 

Hyg. Rund., 1898, vm. p. 161. 



QUALITY O'F WATER . 


150 


TABLE NO. 24 . 

BACTERIAL CONTENT OF RIVER ISAR BELOW MUNICH. 





Number of Bacteria per c.c. 


Year. 

Name of Observer. 

Oberflihring, 

3 Miles. 

Ismaning, 

8 Miles. 

Freising, 

21 Miles. 

Landshut, 

45 Miles. 

1889 

Prausnitz 


6,824 

3,608 


1890 

< < 

3.140 

2,960 

1,510 

910 

1893 

G., L., P.,N.* 

24,100 

15,065 

7,134 

1,976 

1895-6 

Deichstetter, 

Willemar 

1 . 

14,185 

7,893 

2,900 


A few American streams have been more or less perfectly studied 
in this regard. In the sanitary survey made in Ohio of the more 
important streams, the same general relations were noted. Bleile t 
found in every case a marked difference between the bacterial content 
of water above and below the various cities, but this marked increase 
always dropped again to normal in the course of a flow of a number of 
miles, providing there was no new source of pollution. In a general 
way the bacteriological fluctuations correspond to the variation in the 
free and albuminoid ammonia, but in some cases increase in ammonias 
was due to influx of vegetable impurities, in which instance of course 
the bacterial increase was not as marked as after addition of organic 
matter of animal origin. 

The sanitary survey made on the Mohawk and Hudson rivers, 
New York, show a similar relation. The numerical increase in bacteria 
in river-water occasioned by the introduction of the sewage of Albany 
remained evident for a distance of about 11 miles below the city. J 
By far the most extensive study that has yet been made on Ameri 
can streams is that which is now in progress to determine the effect of 
the Chicago Drainage Canal on the water of the Illinois River and so 
indirectly on the Mississippi at St. Louis. These results have not yet 
been published, but through the courtesy of Prof. E. O. Jordan of 
Chicago, one of the analysts who has been engaged in this investiga¬ 
tion, some preliminary data, covering analyses made from May, 1899, 
to January, 1900, (the period of examination before the Drainage 
Canal was opened,) are herewith presented. 

* Goldschmidt, Luxemburger, Frans, Hans u. Ludwig, Neumeyer, Prausnitz. 

f Examination of Sources of Ohio Public Water-supplies, p. 137. 

% Rept. N. Y. State Board of Health, 1892, p. 536. 























SELF-PURIFICATION OF STREAMS. I 51 

TABLE NO. 25 . 

CHLORINE AND BACTERIAL DETERMINATIONS MADE ON WATER IN ILLINOIS RIVER 
AND ITS TRIBUTARIES UNDER AUSPICES OF CHICAGO SANITARY DRAINAGE COM¬ 
MISSION. 


Collecting Stations 

Distance 
from Bridge¬ 
port in Miles. 

Chlorine, 
Parts per 
1,000,000. 

Bacteria per c.c. 

Number of 
Analyses 
Made. 

Bridgeport . 

O 

II9. 2 

1,245,000 

19 

JLockport. 

29 

II 7-4 

650,000 

30 

Desplaines River at Lockport. 


7 . Q 

9 t8o 

2_8 

Joliet. 

33 

104.8 

486,000 

28 

Kankakee River at Wilmington. 


a . zl 

£ OOO 

2-8 

Morris. . 

57 

68.1 

439,000 

26 

Ottawa. 

81 

58.5 

27,400 

26 

Fox River at Ottawa. 


c 0 

6 it TO 

90 

Big Vermillion at La Salle. 


61 2 

** 070 


La Salle . 

95 

46.1 

16,300 

31 

Henry . 

123 

44.2 

11,200 

29 

Averyville . 

159 

40.9 

3,660 

30 

Wesley City . 

165 

40.1 

758,000 

22 

Pekin . 

175 

38.4 

492,600 

29 

Havana . 

199 

36.2 

16,800 

26 

Sangamon River at Chandlerville . . .. 


d. ‘t 

c. ,080 

21 

Beardstown . 

231 

29-3 

14 000 

26 

Kempsville. 

28S 

22.9 

4,800 

19 

Grafton. 

318 

18.3 

10,200 

28 

Mississippi River at Grafton. 


2.8 

7,600 

29 


The extent of natural purification of the Illinois River can be 
observed from the above table. The steady diminution in the amount 
of chlorine is noteworthy all the way from Bridgeport, where a large 
proportion of the sewage of Chicago is present, to Grafton, where the 
Illinois joins the Mississippi. The bacterial reduction is also continuous 
for a distance of over 160 miles, until the river receives at Wesley City 
the large amount of refuse from Peoria. It is to be noted that this 
large additional load of pollution does not increase the chlorine so much 
as it does the bacteria, but this is probably due to the fact that the 
sewage contains a very large amount of manufacturing wastes (distillery 
and glucose refuse). 

The table also includes the tests made on tributary streams, and it 
is strikingly noticeable that in no case but one is the chlorine content 
of such a nature as to add materially to the pollution of the main river. 

169. Causes of Self-purification of Streams. —The explanation of the 
cause of this phenomenon is so complex that no single principle can 
be cited that will apply to all cases. The different factors that are 
operative under changing conditions may be grouped under two heads: 


































152 


QUALITY OF WATER 


(1) Factors concerned in apparent purification, as dilution and 

sedimentation. 

(2) Factors concerned in actual destruction of bacteria, as sun¬ 

light, vital concurrence, unsuitable food-supply. 

Polluted waters may have their germ content reduced per unit of 
volume by the first class of factors without necessarily destroying the 
bacteria associated with the polluting material. 

170. Dilution.—In a purely mechanical manner, polluted material 
is greatly diluted when discharged into a running stream. This dilu¬ 
tion varies greatly with the varying amount of sewage discharged and 
the stage of water in the stream. In rapidly flowing streams this 
factor is more potent than in sluggish rivers. Although a stream may 
not receive any material additions by way of tributaries, yet the volume 
of water in a river is constantly being augmented by the influx of 
ground-water that drains into the drainage-channels from the surround¬ 
ing land, and so the extent of dilution is being gradually increased. 

171. Sedimentation.—Removal of bacteria by sedimentation may 
occur in two ways. There may be a gradual settling of the organisms 
themselves by virtue of their specific gravity, or they may be entangled 
and carried down by the subsidence of suspended particles of silt. The 
latter method is by far the most effective, and in streams is the only 
way in which sedimentation exerts any influence. Subsidence of sus¬ 
pended matter begins to occur whenever the current is lessened, due 
either to expansion of stream or diminished fall per mile. The Spree 
below Berlin illustrates the influence of diminished flow.* From 
190,000 bacteria per cc. found in the river as it emptied into the Havel, 
an expansion of the stream 7 miles broad, the number fell to 9000 as 
it issued from this natural sedimentation basin. 

A peculiar case of sedimentation has been noted by Van’t Hoff, t 
and is utilized in securing the water-supply of Rotterdam from the 
Maas (Rhine). This city is on tide-water, and at flood-tide the 
checking of the current as it meets the sea is so marked that the 
bacterial content of the river is lessened about 50 per cent. During 
this period of partial subsidence the necessary supply is largely 
secured. 

In removing the bacteria from a flowing stream by sedimentation, 
the organisms are not necessarily destroyed. They may be carried to 
the bottom by the precipitation of the inorganic matter and in the 
slimy ooze of the river-bed find conditions more or less suitable for de- 


* Frank, Zeit. f. Hyg., 111. p. 355. 
f Cent. f. Bakt ., XVIII. p. 265. 




SUNLIGHT. 


153 


velopment. No data have yet been collected on this phase of the 
subject, but Russell found in studying the bacterial flora of the sea- 
bottom (Atlantic and Mediterranean) * * * § that the germ content was much 
greater than that of the water, and to a considerable extent was made 
up of species not found in the water above. This would indicate that 
the high content of the mud is not entirely due to sedimentation. 

172. Sunlight.—Direct sunlight has a potent germicidal effect on 
many bacteria, and Buchner t has ascribed a prominent part to this 
factor in explaining the phenomena of self-purification of waters. 
Experimental work has conclusively demonstrated that the germicidal 
effect is caused by the chemical and not the heat rays of the spectrum. 
Not only do the direct rays of sunlight destroy the bacteria, but even 
diffused light in some cases exerts a prejudicial influence. 

Care must, however, be taken in interpreting these data, which have 
been secured for the most part in experiments carried on in various 
culture media; for it has been determined that such media in the pres¬ 
ence of direct sunlight and air may decompose, and antiseptic substances 
as peroxide of hydrogen, be formed. 

Some observers, however, as Frankland, t have carried on their 
investigations in natural waters as well as in culture media; and have 
found, for instance, that anthrax spores are for the most part quickly 
killed in such waters, although other species retain their vitality for 
months; but they are destroyed less rapidly in water than in culture 
media. 

The data collected as to the depth to which this disinfecting action 
of the light is effective are very contradictory. Buchner § found that 
the germicidal influence of the light was very marked when cultures 
were submerged at the depth of 4 to 5 feet, and demonstrable with 
typhoid in agar at 10 feet; but Arloing, || Frankland, IF and Procacci ** 
have all found that an appreciable depth of water (a few inches to a 
foot or so) materally diminished the disinfecting action. The action 
is probably considerably less in rivers than in lakes owing to the in¬ 
creased turbidity of flowing streams. 

Buchner’s ft observations on the increase in bacteria in lake waters 


* Zeit. f. Hyg., xi. p. 165. 

f Cent./. Bakt ., 1892. XII. p. 217. 

% Proc. Roy. Soc., 1893, liii. p. 316. 

§ Cent. f. Bakt.. 1892, XI. p. 7S1; also XII. p. 217. 

|| Arch, de Physiol.. 1886, VII. p. 209. 

If Proc. Roy. Soc., 1893, un. p. 204. 

** Annali d. Inst, d'Igiene Sper. di Roma , 1893, III. p. 437. 
ff Tiemann-Gartner, Das Wasser, p. 579. 





154 


QUALITY OF WATER. 


during the night when compared with observations made, at sundown 
are sometimes cited as confirmatory evidence of this disinfecting action, 
but there are too many disturbing factors that might enter in to mask 
the real effect to rely entirely on observations to prove this point. 
Indeed the observations by Prausnitz * and others on the same river 
(Isar) showed that while frequently a marked decrease was noted in 
some days, they also observed the same on days in which the sky was 
completely overcast. 

From the data already at hand it seems quite clear that the disin¬ 
fecting action of direct light has been considerably overestimated. 
While it is unquestionably operative to some extent, it plays at most 
only a subordinate role. 

173. Vital Concurrence.—Water contains so many other living forms 
than bacteria that it would be surprising if there were not a strong 
competition between the various forms of life represented in the same. 
Different observers t have ascribed to green plant-forms (water-weeds, 
algse, diatoms, etc.) a purifying power, but the evidence as to their 
effect in a polluted stream is far from conclusive. It is true that these 
chlorophyll-bearing organisms do not subsist directly on organic matter, 
and in some cases, as Schenck X has noted, where polluted streams are 
readily purified, organisms of this class are not at all abundant; hence 
their purifying action is by no means satisfactorily proven. 

It is much more probable that the indigenous water bacteria may 
exert a harmful effect on these introduced forms, although this question 
of antagonism is also a disputed question. The water bacteria are able 
to live on a minimum amount of organic nourishment, while the soil 
and sewage species require more nitrogenous food; but it is more prob¬ 
able that any antagonism is due to the action of bacterial by-products 
rather than to living germs themselves. It has previously been shown 
that surface-waters that have been rendered germ-free by filtration 
are not as well suited to sustain bacterial life as when the same waters 
are boiled.§ Wolf, || working in the writer’s laboratory, has shown 
that this phenomenon occurred when filtered waters were heated to 
about 140° F. Above this temperature such waters were apparently 
less toxic. The restraining principle, whatever it is, was evidently 
destroyed above this temperature. 

174 . Unsuit able Food-supply.— The sewage bacteria, and to some 

* Hyg. Rund., 1898, vm. p. 172. ' 

f Low, Arch./. Hyg., 1891, XII. p. 261; also Bokorny, Arch. f. Hyg., 1892, xiv. 
p. 202; 1894, xx. p. 1S1. 

\ Cent. f. Allg. Gesundheitspflege , 1893, xil. p. 364. 

§ Rept. Mass. Board of Health, 1890, p. 593. || Thesis, Univ. of Wis., 1900. 








A ERA riON. 


155 


extent the soil organisms, do not find favorable conditions for rapid 
growth in ordinary waters. This is evident from the numerous experi¬ 
ments that have been made to determine the viability of such organisms 
as the typhoid, cholera, and colon forms (222). When these alone 
are added to water or in competition with other forms, they rapidly 
diminish in numbers. Still the evidence of pollution sometimes dis¬ 
appears in a flow of 6 to 8 hours, and in such cases it could hardly 
be due to their having been killed. In cases of retarded purification, 
as the Seine in France, where pollution is still recognizable after two 
to four days’ flow, this factor might be more effective. 

175. Aeration.—It is a popular belief that aeration greatly improves 
the character of water, but numerous experiments on the effect of 
oxygen and motion, singly and in conjunction with each other, fail to 
show any material effect. Leeds failed to find any difference in 
Niagara water above and below the falls. The experiments by Mills 
on artificial aeration also show but little effect. 

176. Chemical Reaction.—Certain chemical combinations may take 
place in water that will tend to purify the same. The Schuylkill above 
Philadelphia is heavily charged with iron, salts, and acids (due to mine- 
drainage), but in flowing over a limestone reigon the acids in the water 
neutralize the lime salts, precipitating much of the lime and iron, mak¬ 
ing a soft and wholesome water from what was originally unfit for use. 

177. Conclusion.—That flowing streams polluted or contaminated 
in any way do undergo a spontaneous purification there can be no ques¬ 
tion. The factors that have been considered above probably account 
for the most of such change, although the effect of each operative factor 
varies in different cases owing to the change in conditions. 

Naturally no hard-and-fast rule can be given that will apply to all 
conditions, but tlie most definite conclusions that can be drawn from 
the data already at hand indicate that sedimentation and dilution play 
the more important role in the purification of waters. Undoubtedly 
sunlight and the action of other living forms are also operative to some 
extent, but the results already obtained lead to the belief that these are 
only of subordinate influence, especially in the case of streams. 

The important problems for the engineer are: How soon does this 
purification take place? Can streams once polluted be used again with 

safety ? 

From available data it seems evident that a stream once polluted 
with any considerable amount of sewage is unsafe to use for a water- 
supply so long as there is any trace whatever of pollution remaining. 
It is impossible to set a distance limit, or even a time limit of flow 


QUALITY OF WATER . 


156 

(although this would be less objectionable), for such limits would vary 
much in each instance. It has been claimed in England that no 
stream is sufficiently purified by the time it reaches the sea to warrant 
its use, and it is well established that typhoid epidemics have been dis¬ 
tributed for scores of miles down-stream. Disease bacteria can retain 
their vitality in water for a longer period than pollution can be recog¬ 
nized ; * hence the possibility of disease is present whenever it can be 
shown that a stream is polluted with sewage material. 

B. Impounded Surface-waters {Lakes, Ponds , Reservoirs'). 

178. The waters of an open expanse, such as a lake, are less likely 
to show marked pollution than flowing streams, because in relatively 
quiescent waters, solid matter, excepting the finest clays, cannot long 
remain in suspension and the factor of land contamination is of less 
prominence. In large bodies of water, as the Great Lakes, the effect 
of pollution is limited to shore regions, but under certain conditions 
may be considerably extended, as is to be noted along the south shore 
of Lake Superior, where the water is frequently rendered densely turbid 
for a distance of 6-10 miles from shore because of a stratum of tena¬ 
cious red clay along the coast-line. 

At certain seasons of the year, the water-supplies of towns along 
this shore, relying on lake-water, are greatly impaired. The follow¬ 
ing data collected by the writer at Duluth-Superior show the germ 
content of the polluted shore-line in comparison with the crystal-clear 
lake-water. 

TABLE NO. 26 . 


NUMBER OF BACTERIA PER C.C. IN LAKE SUPERIOR AT DULUTH-SUPERIOR. 


Depth at which Sample was secured. 

Distance from Land at which Sample was secured. 

Shore. 

ij Miles. 

5 Miles. 

5 Miles. 

10 Miles. 

S11 r f a rp .... .. 

2457 t 

87 



23 

A C fppt... 


44 

50 

Cl “ . 


16 



60 44 . 


11 

20 

5 

80 “ . 




.no “ . 




6 

V'-' 

Depth of water at different 
stations .. 

3 feet 

very turbid 

60 feet 

80 feet 

90 feet 

faintly turbid 

100 feet 

clear 

Appearance of water at sur¬ 
face . 

cloudy 

turbid 



* Hammerl, Hyg. Rund ., 1897, vii. p. 529. f Average of 14 different samples. 































VERTICAL CIRCULATION IN LAKES. 157 

I 79 * Vertical Circulation in Lakes. ' v —Owing to the fact that the 
maximum density of water is somewhat above the freezing-point 
( 39- 2 F., 4 C.), water in lakes is more or less subject to vertical 

currents that cause the upper and lower layers to mix under certain 
temperature conditions. In large lakes of the temperate type there 
is generally no circulation of the water, as the heavier cold water rests 
on the bottom. In smaller, shallower lakes there are periods of stag¬ 
nation, in which there is no vertical circulation. These occur in 
winter and summer. Between these periods there is an “overturn¬ 
ing,” i.e., a vertical circulation due to temperature changes. In the 
spring, as the surface warms above the freezing-point, the water 
increases in density and therefore becomes heavier. This causes it to 
sink, thus producing vertical currents. In the fall the surface cools 
and the water is apt to be stirred by wind action until the warmer, 
lighter bottom water is forced to rise as the colder surface-water sinks. 

In shallow lakes, small reservoirs, etc., the circulation of the water 
is going on at all times, except while the surface is frozen; but where 
reservoirs are 20 feet deep or so, the phenomenon of stagnation may 
at times occur. 

This is a matter of some importance, as the temperature of a supply 
is affected by these changes. Moreover, if water is drawn from a low 
level in the reservoir, it may be derived from layers that have been 
stagnant for considerable periods of time. 

180. Bacterial Content of Open Surface-waters. —The improvement 
in physical appearance of lake-waters in comparison with rivers reflects 
itself at once in the biological and chemical character of the same. 
Generally speaking, waters of this class contain far less bacteria than 
do running streams. While of course there is no marked uniformity in 
numbers, yet it is rare that waters of this type contain more than a few 
hundred organisms or at most more than a few thousand bacteria per 
c.c. ; and these for the most part are harmless water saprophytes. 

These organisms are more or less uniformly distributed throughout 
the entire mass of the water; but according to Nicholson’s t studies 
made on Lake Mendota under the writer’s direction, the lower strata 
are considerably richer in germ-life than the intermediate layers. The 
surface frequently contains more organisms due tp the effect of dust. 

In summer this bacterial distribution is apt to be obscured through 
the action of wind, light, variation in temperature, etc., but in winter, 
when the water is covered with a mantle of ice and these disturbing 


* See Chapter V in Whipple’s Microscopy of Drinking-water, 
f Thesis, Univ. of Wis., 1900. 




158 


QUALITY OF WATER. 


conditions are more or less thoroughly eliminated, this zonary distribu¬ 
tion is rendered more apparent. In the mud or slime that collects on 
the bottom of lakes and ponds, the bacterial content is greatly 
increased. 

Where surface-waters sustain a copious growth of algae, as is very 
frequently the case, the bacterial content of the water during this state 
may be rendered abnormal through the development of organisms 
living on the organic matter that is derived from the death of the vege¬ 
table organisms. 

181. Natural Purification Processes. —The marked diminution in 
germ content of lake-water as distance from shore increases indicates 
that the natural purification of quiescent surface-waters is also as marked 
as is that of flowing streams. Except in the case of inflow of streams 
of considerable size, the evidence of land-pollution does not extend far. 
The reason for this is, in the main, dilution and sedimentation. The 
disappearance of perceptible currents causes suspended matter to settle 
quickly, thereby reducing greatly the germ content. These organisms 
may be able to retain their vitality in the ooze for some time, but the 
larger proportion found in the lake mud are forms that have evidently 
developed in this habitat (171). 

Lortet* even claims to have found a number of pathogenic bacteria 
at the depth of 120-150 feet in the mud of Lake Geneva, Switzerland. 
The ooze formed from the deposition of sediment in water gradually 
becomes more and more compacted, and, owing to the formation of 
ferrous sulfide, a black gelatinous precipitate is produced that cements 
the particles into a semi-solid sticky mass. Fuller has noted the forma¬ 
tion of this material in the artificial subsidence reservoirs at Cincinnati.f 

Direct sunlight is undoubtedly effective as a factor in purifying 
waters of this class, for quiescent waters are as a rule clearer, and 
therefore the actinic rays would be able to penetrate more deeply 
than in turbid flowing waters. 

182. Influence of Vegetation. —The quality of surface-waters is some¬ 
times affected by the copious development of vegetable life. This is 
particularly apt to occur in relatively shallow lakes where the growth 
of “water-weeds,” as Myriophyllum, Char a , Vallisneria , Ranunculis, 
etc., may be so rank as to accumulate organic matter in large quanti¬ 
ties. While these plant-forms have no direct relation to disease pro¬ 
duction, yet the decay of this vegetable material may seriously affect 
the quality of such water. 


* Cent f. Bakt., 1891, ix. p. 709. 
f Rept. on Cincinnati Water Purification, p. 120. 






ODORS IN WATER-SUPPLIES. 


1 59 


183. Odors in Water-supplies. —It used to be thought that the pres¬ 
ence of any appreciable odor in water was due entirely to the natural 
processes of decay, but in addition to these it is now known that a 
number of living organisms, both plant and animal, give off odors 
during their development, due to the presence of oils formed in the 
cells. Oils of different sorts can be detected by the sense of taste in 
extremely dilute solutions. According to Whipple * the odor of 
peppermint can be noted in water containing 1 part of oil to 50,000,000 
parts of water; clove-oil, 1 to 8,000,000; cod-liver oil, 1 to 1,000,000. 
This explains why the odor from a .relatively small number of some of 
these odoriferous organisms is so manifest. There are a number of 
plant and animal forms that appear so frequently in ponds and reser¬ 
voirs of water-supplies as to warrant specific mention. Besides these 
there is a much larger number of other species that occur less fre¬ 
quently. 

Of the aromatic odors formed, that produced by the diatom, 
Asterionclla , is perhaps the strongest. + Where only a few of these 
organisms are present the odor is aromatic; where more abundant it 
recalls a geranium odor; and where very numerous a distinct fishy 
odor is apparent. Whipple has found by experiment that 50,000 cells 
of Asterionella would produce enough oil so that the dilution was only 
1 : 2,000,000, an amount that is quite within the range of detection. 
Other diatoms are not infrequently found, but their odoriferous proper¬ 
ties are less pronounced. 

Grassy odors are caused mainly by the blue-green algae, the 
Cyanophycece. The most distinctive member of this group is Auabcena. 
When abundant, the water has a taste resembling green corn. Vege¬ 
table odors ai*e caused by the diatoms, Syne dr a and Melosira. With 
the former, 5000 cells per c.c. suffice to produce a distinct odor. 
Whipple has often found in the Brooklyn supply as many as 15,000- 
20,000 of these organisms per c.c. 

Of all defects of this class in water, fishy odors are the most objec¬ 
tionable. One of the animal forms belonging to the protozoa, Uro- 
glena, produces an odor resembling cod-liver oil; while another, 
Synura , recalls the odor of ripe cucumbers. Troubles of this character 
have appeared several times in the Boston water-supply. At first they 
were ascribed to Spongilla, the fresh-water sponge, but later they were 
traced to Synura, which was found to be developing in large numbers 
in Lake Cochituate under the ice. 

* Microscopy of Drinking-waters, p. 123. 

f 1 . c., p. 125. 




l6o QUALITY OF WATER. 

It might naturally be thought that these troubles, being due in the 
main to vegetable growth, would be more apt to prevail during the 
summer months than at other seasons, but such is not necessarily the 
case.* Of the algae, Anabccna is apt to occur most frequently from 
July to September. Pediastrum , Raphidium, Scene dc sinus, Closterium , 
and Staurastruin are most numerous in July and August, but the 
diatoms, as Asterionella, Melosira, Synedra, and Tabellaria , are often 
more abundant in early spring or late fall than at other seasons. The 
protozoan forms ( Dinobryon , Peridinium , and TracJielomonas') occur 
most commonly in March, July, and August. 

Anabcena is generally confined to standing surface-waters. The 
desmids and diatoms are often found in open reservoirs of ground- 
waters and in all surface-waters. The diatom, Synedra , is more char¬ 
acteristic of running water, as rivers and brooks. 

Troubles from bad or unpleasant odors in water-supplies are very 
much more apt to occur in open surface-waters than any other; hence 
impounded supplies may develop these abnormal conditions at times. 
Of 71 supplies examined by the Massachusetts Board of Health, a bad 
taste was noted in 45, and of these two-thirds gave serious trouble. 

C. Ice Supplies. 

184. Influence of Freezing on Bacterial Life. —The quality of ice is 
dependent primarily upon the character of the water before it is frozen. 
It is true that some of the grosser solid impurities are expelled from 
water, especially if congelation takes place gradually, but it does not 
follow that ice made from polluted water is safe for human use. 

Hot only does the examination of ice show that it is generally 
poorer in germ-life than the subjacent water beneath, but experimental 
tests on the resistance of bacteria to freezing indicate that many forms 
and more particularly disease species are capable of retaining their 
vitality for many months. 

Prudden,t Sedgwick,^ and Park § have found that the typhoid 
bacillus is capable of retaining its vitality for at least three months 
when frozen, although there was a rapid diminution in number of 
organisms immediately after freezing. 

In the process of freezing from 60-90 per cent of the contained 
organisms are killed, although many vegetative as well as spore-bear- 

* Parker, Mass. Bd. Health, Exam, of Waters, 1890, p. 597. 

\ Med. Rec., March 26, 1887. 

% Science , March 23, 1900. 

%Journ. of Boston Soc. Med. Sc. f April, 1900. 




SUBTERRANEAN WATERS. 


161 


in g forms are able to resist freezing for a while at least. While from 
experimental work it has been definitely shown that typhoid and othei 
pathogenic organisms are able to retain their vitality for long periods 
of time when frozen, still there is no authenticated case in which 
typhoid epidemics have been traced to the use of impure ice, although 
intestinal disturbances are known to have been caused in this way.* 

\ 

SUBTERRANEAN WATERS. 

185. Change in Quality Due to Percolation. —That portion of the 
rainfall that finds its way into the soil is rapidly changed in quality by 
percolation through the various soil-layers. As it flows through the 
soil toward the ground-water level it loses the larger portion of the 
impurities derived from the air and the soil surface, but at the same 
time it absorbs other substances from the layers through which it 
passes, so that in general, the quality of subterranean waters is 
materially different from those of surface origin. 

To some extent the gaseous content of rain-water is changed as it 
courses through the soil. The particles of suspended matter (soot, 
dust, and germ-life) that are absorbed from the air, together with the 
organic matter and bacteria derived from the upper soil-layers, are 
readily removed in the percolation process, so that at a depth of a few 
yards at most the germ-life of the surface of the soil and all its attend¬ 
ant impurities have been eliminated. 

On the other hand the percolating water dissolves certain inorganic 
elements, and especially by virtue of the C 0 2 , which it has absorbed 
from the air, this solvent action is greatly increased.f In this way the 
salts of lime and magnesia are rendered soluble, making hard waters, 
while other mineral elements, such as the silicates, are also carried more 
readily into solution. This action increases materially the total solids 
of a water, more particularly those of an inorganic character. Subter¬ 
ranean waters therefore carry a load of soluble solids, while the solids 
of surface-waters are more largely in suspension. In regions rich in 
humus the ground-water may contain a large amount of organic as well 
as inorganic constituents. 

Not infrequently such waters may also contain ferrous salts. In 
the presence of humus and absence of oxygen, the sulfates may be 
reduced to hydrogen sulfide, and the nitrogen compounds to ammonia. 
These iron-containing ground-waters are of not infrequent occurrence; 

* Sedgwick, Science, March 23, 1900. 

f Pure water dissolves about 1 part in 10,800 of carbonate of lime, while the same 
saturated with carbon dioxide is able to render soluble about 1 to 1000. 




QUALITY OF WATER . 


162 

and in many cases they are otherwise desirable, but the presence of the 
iron impairs the quality of a supply for drinking and domestic use, not 
so much on hygienic grounds as because of its physical appearance. 
Moreover, in such waters, the so-called iron fungus, Crenothrix poly- 
spora, is very apt to become established, in which case the iron is 
oxidized from a ferrous to a ferric form. Inasmuch as this organism 
does not require light for its growth, it is able to grow in covered 
reservoirs and pipes. 

186. Purification of Water in the Soil. —By the operation of natural 

processes in the soil, water is purified in passing from the surface to 
the ground-water level. The forces concerned in this change are 
physical, chemical, and biological. The larger part of the suspended 
matter is removed by filtration in a purely mechanical manner. There 
is also an attraction for substances in solution, as is evident from the 
fact that the color of water due to dissolved matter is removed in part 
at least by percolation through soil. 

Chemical changes may also be caused by the action of one sub¬ 
stance or another, precipitating or dissolving the same, but the most 
effective transformations are those that are induced by biological 
causes, viz., the micro-organisms present in the soil-layers. In the 
upper layers, organic matter, vegetable or animal, undergoes fermen¬ 
tation, putrefaction, or decay, with the result that the nitrogenous 
organic substances are gradually converted into soluble condition, 
generally ammonia compounds. The carbonaceous elements are 
changed into carbon dioxide, water, and organic acids. 

When material containing nitrogen has been converted into 
ammonia compounds, it is then acted on by the nitrifying bacteria, 
forming first nitrites and then nitrates. 

These mineralizing processes, which are really oxidation changes, 
take place more rapidly in the superficial layers of the soil, where 
oxygen is more abundant. Temperature and character of the soil also 
exert- an influence on rate of change. 

In swampy regions containing a large amount of humus, and there¬ 
fore so acid as to inhibit the development of the nitrate-producing 
bacteria, the nitrogenous material accumulates as ammonia products 
rather than as nitrates. 

187. Capacity of Soil for Purification. —The purifying action of the 
soil is not unlimited, and under certain artificial conditions largely 
ceases to be operative. Naturally, the action of any pollution is inter¬ 
mittent, the offensive material being discharged on the surface at inter¬ 
vals, between which the natural purifying forces are operative. This 


S UB TERRA NEA N JVA TERS. 


163 

condition is essential to adequate purification. Under artificial condi¬ 
tions occasioned by man’s presence, this intermittent action may be 
suspended. If, therefore, sewage is discharged continuously on to the 
surface of the soil, even though in small amounts, the action of the 
natural purifying processes is disturbed, and the result is that the soil 
becomes saturated with organic matter which is not converted into the 
harmless substances that would naturally be produced as a result of 
the operation of soil processes. It is in this way that the soil of thickly 
populated areas like citiesdoses its property of spontaneous purification, 
often to such an extent that the ground-water is rendered impure. 
Under such conditions, while the organisms of disease may be held 
back by the soil layers, the soluble products of organic decay are able 
to percolate into the ground, thus making it especially difficult to 
determine the wholesomeness of such water where reliance is placed 
on chemical examination alone. 

188. Extent of Filtration Necessary to Effect Purification. —The dis¬ 
tance through which the water must pass before it is sufficiently purified 
for potable purposes is a question of very considerable importance. 
Judging from the higher typhoid mortality rates of populations using 
shallow wells in comparison with those utilizing a supply from a deeper 
source, it is evident that efficient purification is often not reached in 
shallow wells. This may of course be due in some cases to direct 
pollution. Not infrequently it may happen, where the ground-water is 
subject to considerable oscillations in level, that at high stages this 
generally sterile water layer comes in contact with soil that is not bac- 
teria-free. This condition might possibly arise in cities, especially 
where the land has been filled in, and where decomposing organic 
matter is some distance below the soil surface. 

The depth necessary to insure efficient purification will also vary 
with the filtering power of the soil. Loose, sandy, or gravelly soil hav¬ 
ing larger pore-spaces will permit of more ready filtration than compact 
clay loams. Pfuhl * has determined, by adding a culture of some easily 
demonstrable organism like B. prodigiosus to water in a well, that 
there can be a lateral movement into the ground for 10 feet or more. 

Again there is to be mentioned the possibility of direct rifts or 
channels existing in the soil or rock. Holes made by animals (rats 
and larger rodents), earthworms, Crustacea, etc., frequently permit of 
direct passage of unfiltered water to considerable depths. A number 
of cases of wells and springs have been recorded where the germ con¬ 
tent was so high and of such a character as to leave no doubt but that 


* Pfuhl, Zeit. f. Hyg.y xxv. p. 549. 






164 


QUALITY OF WATER. 


there was a direct connection with the surface.* * * * § Generally this con- 
dition is more likely to prevail along faulting cracks in rock layers 
than in soil, or in limestone regions where subterranean channels have 
been dissolved by the water. The classical case of the Lausanne, 
Switzerland, epidemic, + where the village well was infected from a 
polluted brook over a mile distant, but which had an underground 
connection with the well, is a striking illustration of the unreliability 
of natural purification through soil layers. Gaffky J showed that the 
Wittenberg typhoid epidemic in 1882 was due to infection of an open 
well from vaults 50 feet distant. The stratum in this case was gravel. 

Thoinot and Brouardel § traced a typhoid epidemic in Havre to 
pollution through 80 feet of chalk to a clay substratum where the water 
appeared as a spring. Such cases happily, however, are exceptional. 
In general, ground-water supplies are the most reliable of any. For 
individual use and for small municipalities, they will always remain the 
principal source of supply, and their use could undoubtedly be extended 
in some cases to larger cities. 

189. Spring-waters.—In the popular mind springs are supposed to 
represent the purest of supplies, but under certain circumstances this 
type of ground-water may not be wholly pure. They are produced by 
percolating rain-water flowing along an impervious stratum until it finds 
an outcrop to the surface. Often in mountainous districts the depth 
and thoroughness of percolation over and through rock masses is so 
limited that the water may not equal in purity the normal ground- 
water. Generally, spring-waters before exposure to surface of soil 
are relatively deficient in micro-organisms, as they represent filtered 
waters, but as they appear at the surface, the water comes again in 
contact with organic matter and soil bacteria, and may thus receive a 
considerable quota of organisms from this source, although generally 
the germ content of unpolluted springs is below 100-200 per c.c. || 

While spring-water usually has a low initial bacterial content, the 
organisms contained in such waters possess the property of very rapid 
multiplication during storage. According to Miquel 1 this rapid but 
transitory power of development characterizes the bacteria of spring- 
waters in contradistinction to the slower and more persistent growth 
that occurs in impure waters. 

-* —— " -- 1 ■ ' 1 

* Tiemann-Gartner, Das Wasser, p. 523. 

f Deutsch. Arch. f. Klin. Med.. 1893, Bd. 11. 

t Gaffky, Mitt. a. d. Kais. Gesundheitsamte, 1884, 11. p. 413, 

§ Thoinot, Bacteriology, p. 62; also Ann. Fast.. 1889, HI. p. 145. 

|| Tiemann-Gartner, Das Wasser, p. 492. 

T Manuel pratique d’Analyse bact. d. Eaux, 1891, p. 146. 




SUBTERRANEAN WATERS . 


I6 5 


190. Well-waters.— It not infrequently happens that there may be 
several impervious geological layers' superimposed on each other that 
serve to collect the water from different areas. Under such circum¬ 
stances the upper stratum will retain the local ground-water of the 
region, while the more copious supply beneath is the result of percola¬ 
tion from a larger and perhaps distant source. Shallow wells often 
strike only the surface ground-water, which is sometimes of poor quality, 
while the water of deep wells which tap the larger, more universal 
supply in the rock is usually more thoroughly purified. Shallow wells 
dug in the soil and walled up dry are often to be found in the more 
crowded portions of cities. Generally these are sunk in soil that is 
more or less thoroughly impregnated with organic refuse, so that the 
water in the same is often in a polluted condition, not having been 
purified by its passage through a shallow, and at the same time con¬ 
taminated, soil stratum. 

Then, again, wells of this character practically serve as drainage- 
basins for the thickly populated areas above them, and when walled up 
dry, seepage from the soil is carried directly into the same. The 
influence of near-by closets and vaults is thus not infrequently to be 
observed. Cesspools are particularly dangerous, because they contain 
so much water which must find its way into the soil by percolation. 
Just how far wells of this character should be placed with reference to 
vaults and cesspools depends upon the character of the soil and the 
contour of the surface. In shallow wells where the ground-water 
layer may be lowered through pumping, the zone of influence may be 
considerably widened. Pfuhl places the average distance at 100 feet, 
but it is evident that no exact limit can be drawn. Where the ground- 
water lies near the surface the distance should be manifestly increased 
to a maximum limit. Not infrequently open wells of this class may 
be polluted directly from the surface, unless graded up so as to carry 
off the local drainage. Wells of such character frequently serve as 
disseminators of water-borne diseases. Their condition is at once 
betrayed by a chemical or bacterial test. They contain large numbers 
of bacteria, and the presence of gas-producing, indol-forming organisms 
at once indicates their impure condition. Such wells generally have a 
high chlorine content, as this element continues to increase with the 
growth of population, and the presence of nitrogen in nitrous and nitric 
forms and considerable quantity of the ammonias is further proof of 
pollution with organic refuse. 

The better class of wells that are sunk into the permanent ground- 
water are either drilled or driven. In these the sides of the wells are 


QUALITY OF WATER. 


166 


made impervious to seepage by iron casing, so, that barring pollution 
from direct surface-drainage at the top, the only ordinary chance for 
contamination is in tapping an impure ground-water. 

191. Bacterial Content of Wells. —While the ground-water is pre¬ 
sumably free from bacteria, or at least very nearly so, water as it is 
taken from wells almost always has an appreciable germ content. In 
the case of shallow, dug wells where opportunity for infection from 
above or seepage from sides is present, and where the temperature of 
the considerable mass of water is such as to permit more rapid bacterial 
growth, it is not at all uncommon to find thousands of organisms 
per c.c. The infiltration of organic matter aids materially in the 
development of this germ life. 

In the better type of wells, drilled or driven, the germ content is 
subject to wide variation. Normally where all opportunity for external 
pollution is excluded, the number of bacteria per c.c. is very small. 
Frankland found in some of the deep wells in the chalk in England 
only six bacteria per c.c., but often where the most careful precautions 
are taken in securing samples a much larger number is to be found. 
Sedgwick and Prescott* found the following numbers in a series of deep 
wells in Massachusetts examined by them: 

No. of Bacteria per c.c. 


Well 100 feet deep. 30 

Well 193 “ “ 269, 254 

Well 213 “ “ 101, 106 

Well 254 “ “ 150, 135 

Well 377 “ “ 48. 54 

Well 454 “ “ 205, 214 


These waters were characterized by the absence of liquefying bac- ' 
teria and the abundance of pigment-forming species. Similar results 
have also frequently been recorded by others. The following summary 
from Tiemann-Gartner’s book on Water + gives an idea of average' 
conditions. 

TABLE NO. 27 . 


SUMMARY OF OBSERVATIONS ON BACTERIAL CONTENT OF WELLS. 


Locality Observed. Observer. No. per c.c. 


Mayence . 


( 34 wells 

in 64 had less 

than 100 



1 bd 





500 

Stettin. 


27 

« 4 

“ 47 

4 4 

4 4 

4 4 4 < 

Steinberg. 


9 

4 < 

“ 10 

4 4 

4 4 

4 4 4 4 

Kaiserslautern. 


59 

4 < 

“ 78 

4 4 

4 4 

IOO 

Leitmeritz. 


12 

t 4 

“ 59 

4 4 

4 4 

“ 500 

Gotha. 


j 34 

( 4 

“ 53 

4 4 

4 4 

“ IOO 



l 50 


“ 53 


< 4 

500 

Kiel. 


5 i 

4 4 

“ 179 

4 4 

1 < 

4 4 4 4 

Hbchst . 


M 

O 

CO 

4 4 

“ 118 

4 < 

4 4 

< 4 4 4 


*26 Rept. Mass. Bd. of Health, 1894, p. 435. 
f Das Wasser, p. 489. 






























SUBTERRANEAN WATERS. 


16/ 

It is evident from the above that while the average conditions in 
well-water do not show a high germ content, yet even good wells often 
contain a considerable number of bacteria. 

Of course it at times happens that even deep wells may receive 
ground-water that has not been wholly purified. Pfuhl* cites an 
instance where pollution occurred after passing through 180 feet of 
gravel, but these cases must be exceptional. From whence do these 
organisms then come ? In all probability infection occurs at the time 
of digging the well. The machinery used in the digging is far from 
being bacteriologically clean, and in this way the water is seeded from 
the beginning. Many of the species are able to grow even in pure 
water, and the result is that some development occurs, so that various 
forms persist in the water. The following observations made by Hast¬ 
ings and the writer on newly drilled wells where chance for contami¬ 
nation was absolutely excluded point to this conclusion: 

WELL NO. I DRILLED IIO FEET IN DRIFT (GRAVEL, SAND, ETC.), JULY, 1899. 


Number of bacteria per c.c. July 24, 1899.10,080 

Oct. 6, 1899 . 2,050 

Dec. 14 1899. 380 

March 29, 1900. 18 

WELL NO. 2 DRILLED 60 FEET IN SAME FORMATION, NOV., 1899. 

Number of bacteria per c.c. Dec. 14, 1899.11,450 

March 29, 1900. 570 


Both of these wells contained an enormous number of liquefying 
bacteria at the beginning, but non-liquefying species predominated 
later. 

Frankelf has also demonstrated that this infection occurs from 
without by disinfecting a well with a mixture of carbolic and sulfuric 
acid; then by removing the chemicals by long-continued pumping. 
Wells so treated remained germ-free for 6 -y days, but ultimately 
became invaded from above. 

192. Effect of Pumping. — Bacterial growth can go on at surprisingly 
low temperatures; and in deep wells in the ground where the water is 
in the neighborhood of 48-50° F., the conditions are such that multi¬ 
plication of germ-life readily occurs. When a considerable volume of 
water is present in the well, the distribution of bacterial life throughout 
the same can readily occur. Under such circumstances the number of 
organisms per c.c. in the water can often be greatly reduced by pump¬ 
ing out the standing water and allowing fresh quantities of germ-free 
ground-water to percolate into the reservoir. Even with long-con- 

* Arch. f. offentl. Gesundheitspjlege in Elsass-Loth., 1895, XVI. Heft 2. 
f Zeit. f. Hyg., VI. p. 23. 











QUALITY OF WATER . 


168 

tinued pumping it is practically impossible to remove all bacteria 
adherent to the sides of well and pump. Maschek records an instance 
where 31,500 gallons of water were pumped from a well in 12 hours, 
and the germ content was reduced from 2750 to 1064; in another case 
it fell from 458 to 68 when 1600 gallons were removed. 

Gruber * carried on uninterrupted pumping experiments on a well 
for several days with the following results: 

Beginning of test.several thousand per c.c. 

8 days’pumping.472 “ 

14 “ “ . 22 “ 


193. Effect of Organic Nutriment on Growth of Water Bacteria.—The 

ability of bacteria to thrive in well-waters depends in large degree on 
the amount of nutriment they find in such a habitat. Rubner + added 
to a well a small quantity of meat extract and then determined its 
effect on germ-life. A quantity that was only able to increase the 
amount of oxygen consumed by 1-2 mg. caused the germ content to 
rise from 10,000 to 50,000 and finally to 170,000, at approximately 
which point it remained for some weeks. This indicates that if a well 
is so poorly constructed as to permit of the percolation of soluble organic 
matter, the conditions are such as would favor growth of organisms in 
the same. 

194. Artesian Wells.—In flowing wells where the flow is always 
outward it would be difficult to imagine how infection from outside 
might occur, and yet a bacteriological examination of such waters not 
infrequently reveals the fact that they may contain some bacteria, 
although generally much less than ordinary wells. Such a condition 
would naturally seem at variance with the idea that the ground-water 
is practically sterile; but when one recalls that in a number of these 
deep subterranean supplies Crustacea and small fish X have been found 
in some cases, it is evident that a deep supply does not necessarily 
mean that the water has really been filtered through a very deep layer 
of soil or rock. Russell found at Dubuque, la., in several artesian 
wells over 1500 ft. deep from 30-90 organisms in one, and 300-400 
in another. Several analyses were made of these waters at different 
times with corroborative results. 

It often happens that water from deep wells and springs contains 

* Deutsche Vierteljahrschr. f. offentl. Gesundheitspjlege , xxv. p. 415. 

f Arch. f. Hyg ., XI. p. 365. 

X In the artesian wells. 180 feet deep, situated at Biskra in the Sahara desert, 
mollusks and small fish are found at times. 









EFFECT OF STORAGE. 


169 


nitrites in quantities that would be sufficient to condemn a water if it 
was from a shallow well or a surface-water. This condition may, 
however, have no significance, as it may be brought about by a reduc¬ 
tion by various causes of the nitrates in the deeper layers of the soil. 

EFFECT OF STORAGE AND DISTRIBUTION ON QUALITY. 

195. Improvement of Water by Storage.—In most cases in municipal 
supplies it is necessary to store the water in reservoirs of varying size, 
so as to provide against contingencies. Under such conditions the 
water is sometimes subject to changes, some of which improve while 
others impair the quality of the supply. 

The changes that result in an improved condition occur generally 
with waters of surface origin rather than with spring- or ground-waters. 
In the storage of waters of this class sedimentation is effective in 
eliminating much of the suspended matter, including living organisms, 
as well as a portion of the dissolved organic matter. Where consider¬ 
able mineral matter is in suspension, as in many rivers, especially during 
flood seasons, the degree of purification by subsidence is even greater 
than where the suspended solids are less. St. Louis derives its supply 
from the Missouri River, which at some seasons of the year may contain 
nearly 2 per cent by volume of suspended solids. Nearly 95 per cent 
of this is precipitated in the storage-reservoirs during 24 hours, with the 
result that the germ content is greatly reduced. 

The factors operative in the spontaneous purification of lakes are 
also of value in the changes induced by storage in reservoirs. 

The color of waters, especially when due to organic matter, is 
lessened by storage, although this bleaching action of the sun’s rays 
does not extend rapidly to any great depth. 

196. Impairment of Water by Storage.—Surface-waters, however, 
may be impaired in quality by storage under certain conditions. A 
marked effect is apt to arise from the stagnation of the water. Under 
certain temperature conditions, the water in large reservoirs during 
quiescent periods * does not circulate vertically and therefore the lower 
layers become stagnant. If the bottom of such reservoirs contains 
considerable organic matter, as is generally the case where water is 
impounded in artificially made lakes, then the dissolved oxygen is 
rapidly exhausted, causing the death of all organisms incapable of lead¬ 
ing an anaerobic existence. Such waters frequently acquire bad odors. 
The following observations by Whipple f show this variation. 

* This is especially liable to occur when reservoirs are covered with ice. (Drown, 

24 Mass. Bd. Health, 1892, p. 333.) 

f Whipple. Microscopy of Drinking-water, p. 137. 





QUALITY OF WATER. 


i 70 


TABLE NO. 28 . 


DISSOLVED 

OXYGEN IN LAKE COCHITUATE, MASS. 



Per cent of Saturation. 


Aug. 16, ’91. 

Sept. 28, ’91. 

Surface.... 


90 

10 feet deep.... 

. 84 

8l 

20 “ “ .„.. 


33 

40 “ “ _ 


8 

50 “ “ - 


0 


If the organic matter in the upper soil layers is removed before 
impounding these surface-waters, this difficulty does not occur, a con¬ 
dition that generally obtains in lakes that have a gravelly or sandy 
bottom. 

Ground-waters and those which have been purified by artificial filtra¬ 
tion are not improved by storage in open reservoirs. In fact waters 
that have been thus purified by filtration through soil-layers and the 
germ content thereby greatly reduced are much more liable to deterio¬ 
rate than grow better by storage.* A supply that is drawn from both 
ground and surface sources, as in the Brooklyn supply, is much more 
apt to give trouble than a pure ground-water, as the admixture of sur¬ 
face-water will generally seed the water with living organisms, which 
are able to develop rapidly in such waters. 

When purified waters are allowed to stand, the bacteria are able to 
develop prolifically; and while this development has no special signifi¬ 
cance from a sanitary standpoint, because these organisms are generally 
the normal water bacteria, still it does not improve the water in any 
Vvay. 

Ground-waters, owing to their passage through the soil, contain 
considerable soluble mineral matter, and therefore such waters are well 
adapted to the development of some kinds of plant-life. Whipple t 
thinks this is less likely to happen in a new reservoir than in one which 
has been long in use. The accumulation of organic sediment on the 
bottom of the reservoir is very apt to facilitate the development of this 
type of microscopic life (183), of which the diatom, Asterionella , is 
perhaps the most undesirable representative on account of the marked 
odor that it produces. Waters of surface origin that have been filtered 
act in this respect like a ground-supply. 

This development of algae can be prevented by covering the reser¬ 
voirs, as direct sunlight is necessary for the multiplication of these green 


* Water-supply of Brookline, Mass., 19 Rept. Mass. Bd. Health, p. 89. 
f Microscopy of Drinking Water, p. 141. 










EFFECT OF DISTRIBUTION ON QUALITY . 171 

plant-forms. v: If the impounded water cannot be protected from the 
sunlight by covering the reservoirs, it will be of some service to have 
che basins as deep as possible, so as to check the growth of these 
organisms. 

In covered reservoirs, however, certain ground-waters may also be 
affected. Fungi, bacteria, and animal forms, living as they do on 
organic material, do not need sunlight. Hence they might find in 
coVered reservoirs a favorable habitat, but as animals generally live 011 
algae, their presence is determined by this fact. The most important 
organism of this class is Crenothrix , the iron bacterium, which often 
grows so luxuriantly in waters containing iron and organic matter as 
frequently to clog the service-pipes by the accumulation of vegetable 
growth. Sometimes this water-pest flourishes to such an extent as to 
necessitate a change in base of supply, as in Berlin, or the introduction 
of a method of treatment that will eliminate the iron before the water 
flows into the distributing-mains. 

197, Effect of Distribution on Quality. — In distributing - mains 
changes in character of water may also occur. The temperature varies 
considerably during passage through pipes, and this has some effect on 
the living organisms of the same. The action of water on the pipes is 
considerable, especially if derived from a supply that is poor in lime 
and magnesia salts. Unless protected, the pipes are liable to rust and 
the so-called iron “tubercles ” form on the inner surface. In “dead 
ends,” owing to the stagnation in current, the water may acquire a dis¬ 
tinct’ chalybeate taste and appear unsightly from flakes of iron-rust. 
This condition is much aggravated if the water itself contains iron in 
solution, in which case the iron bacteria ( Crenothrix ) are able to 
thrive. Certain kinds of waters, as those rich in C 0 2 or organic acids, 
may exert a solvent action on service-pipes if they are made of lead to 
such an extent as to produce lead poisoning. This trouble occurs 
.most frequently in connection with peaty waters. 

Most other microscopic organisms are reduced in number in the 
distributing-pipes. If the source of supply is from reservoirs or surface 
bodies, it is apt to contain algae which are unable to live in darkness. 
Such organisms therefore die and decay rapidly in the pipes, and if 
sufficiently numerous undesirable odors may be imparted to the water, 
besides furnishing food for bacteria. Many organisms are deposited by 
sedimentation, particularly in pipes on an “up-grade” or in high 

* Sometimes a limited light through the roof of the reservoir cover will permit 
certain species, as Chlorococcus , Asterionella , Melosira , and Synedra , to develop, as 
Was the case at Dedham, Mass., where the supply was drawn from a covered well. 




QUALITY OF WATER. 


172 

buildings. Animal forms, living as they do on organic matter, are able 
to grow under such conditions, and in waters- supplied from surface 
sources it is not uncommon to find the inner walls of the mains covered 
with a considerable layer of “pipe-moss ” which may be made up of 
sponges, Protozoa , and Bryozoa. Ground-waters are not so likely to 
be troubled. 

Changes occur in the bacterial content of water during distribution, 
but sometimes they are increased and again they may be diminished. 
There does not appear to be any well-defined law regarding their 
action. 


LITERATURE. 

Most of the text-books of a general character that are mentioned unaer 

the Literature of Chapter VIII also include the subject of quality of water. 

The following papers also treat the different phases of the subject of 

quality of water. 

Rafter, Geo. W. Lake Erie as a Water-supply for Towns along its Borders. 
Buffalo Soc. Nat. Sciences, Jan. 13, 1896. 

Hazen and Reynolds. The Water-supply of Chicago. Amer. Pub. Health 
Assn., 1893, p. 146. 

Sedgwick, W. T. Protection of Surface-waters from pollution. Journ. N. E. 
W. W. Assn., Mch. 1897, p. 245. 

Frankland, P. F. The Present State of Knowledge concerning the Self-puri¬ 
fication of Rivers. Eng. News , 1891, xxvi. p. 218. 

Currier. Self-purification of Flowing Water and the Influence of Polluted 
Water in the Causation of Disease. Trans. Amer. Soc. C. E., 1891, 
xxiv. p. 21. 

Fitzgerald. Lake Temperatures. Trans. Am. Soc. C. E., 1895, xxxiv. p. 67. 

Leeds. Report on Odors and Tastes of Brooklyn Water. Eng. News, 1897. 
xxxviii. p. 13. 

Farlow, W. G. Relation of Certain Forms of Algae to Disagreeable Tastes 
and Odors. Science, 1883, 11. p. 333. 

Forbes, F. F. Relative Tastes and Odors Imparted to Water by Algae and 
Infusoria. Journ. of the N. E. Water-works Assn., 1891, vol. vi. 

Jackson and Ellms. Odors and Tastes of Surface-waters with Special Refer¬ 
ence to Anabaena. Tech. Quart., December, 1897. 

Whipple, G. C. Report on Organisms of the Boston Water-supply. 19 
Rept. of the Boston Water-works, 1894. 

Calkins, Gary N. Study of Odors observed in the Drinking-waters of Mass. 
24 Rept. Mass. Bd. Health, 1892, p. 355. 

Parker, G. H. Rept. upon the Organisms (excepting Bacteria) found in the 
Waters of the State. Exam, of Water-supplies, 1800, p. S7Q. 
Mass. Bd. Health. 

Winogradsky, S. Ueber Eisenbakterien. Bot. Zeit, 1888, Bd. 46. 

Zopf, W. Unters. u. Crenothrix polyspora, 1879. 

Giard, A. Sur la Crenothrix Kuhniana; la cause de l’infection des eaux de 
Lille. Compt. rendu l’Acad. d. sc., 1882, xcv. p. 247. 

Sedgwick, W. T. On Crenothrix Kuhniana. Tech. Quart., 1890, p. 338. 


CHAPTER X. 


COMMUNICABLE DISEASES AND WATER-SUPPLIES. 

198. Relation of Water-supplies to Disease Dissemination.—The key¬ 
note of sanitary science, so far as applied to the investigation of water 
problems, is to be noted in the relation that exists between com¬ 
municable or transmissible diseases and public water-supplies. That 
disease-producing germs may find their way into the human body 
through water and so possibly cause outbreaks of different maladies has 
been known from time immemorial. The ancient Romans appreciated 
this when they spent so much time and labor to bring their water- 
supplies through their magnificent aqueducts from beyond the reach of 
pollution. 

The most important question to be considered in connection with 
any water-supply is: (1) whether it is wholly free from the possibility 
of distributing disease; (2) whether it is likely to remain in such a con¬ 
dition. These are questions of much more importance than economy 
in securing or distributing water, and should therefore first engage the 
attention of the sanitary engineer. Of the various maladies that are 
transmissible from person to person, only a limited number are likely 
to be distributed through the medium of water. These are known as 
water-borne diseases in contradistinction to those that are disseminated 
through the air or find an entrance by means of Wounds. 

199. The Germ Theory of Disease.—The germ theory of communi¬ 
cable diseases is now so definitely established that it is unnecessary to 
present proof in detail that the various maladies of this class are caused 
by the introduction of living organisms from outside of the body. In 
connection with this theory, two schools have arisen, one holding to 
the idea that each disease has a specific cause, an organism which alone 
is responsible for the occurrence of the pathological condition. The 
other adheres to the hypothesis that the production of a diseased state 
requires more than the introduction of the germ associated with the 
malady. According to this school the organism must find its way into 

173 


1 




1 74 COMM UNICA BLE DISEA SES A ND WA TE E-SUP PLIES. 

a susceptible soil, under conditions which favor the production of the 
diseased state. 

It is at once evident that these theories have a direct bearing upon 
questions relating to sanitary engineering. If the introduction of the 
specific germ of cholera is all that is necessary to provoke an attack ol 
that disease, it is more than ever necessary that all cholera organisms 
should be prevented from finding their way into waters used as public 
supplies. 

200. Specific Nature of Water-borne Disease Germs.—In the case of 
most water-borne diseases, it is quite generally admitted that the causal 
organism is more or less sharply differentiated from other bacteria. In 
one case, i.e., typhoid fever, the specific nature of the organism is not 
defined with so much certainty. Bacillus typhosus, the typhoid fever 
bacillus, is closely related to the common intestinal organism, Bacillus 
coli communis; and by some it is held that these are merely two 
varieties of the same germ.* The preponderance of evidence, how¬ 
ever, is generally believed to be in favor of the specific nature of the 
two organisms; yet from the engineer’s point of view it does not matter 
much, for any drinking-water that contains evident traces of intestinal 
discharges certainly should not be regarded as a safe supply, even ii 
the possibility of human wastes finding their way into the same be 
wholly excluded. 

201, Diseases Due to Parasitic Intestinal Worms.—Whether feca? 

matter from distinctively animal sources should be permitted to pollute 
drinking-water is a somewhat different question, for the diseases inch 
dent to man that are most frequently spread by means of the water- 
supply do not normally occur among animals, yet the possibility exists 
that larvae and eggs of parasitic worms may find their way into water 
through discharges of animals. In a number of cases these parasites 
are common to both man and some of the lower animals, and hence 
the danger from this source is evident. Among the more common 
parasitic worms that affect man are the pork tape-worm {Tania solium ), 
the round worm (A scar is lumbricoides), the thread-worm ( Oxyuris 
vermicularis'), and the worm causing pernicious anaemia ( Anchylosto - 
mum duodenalc). These worms, while affecting the human species, 
also find lodgment in some of the lower animals. In such cases their 
intestinal contents may contain eggs which may thus find their way 
into waters through pollution of the same with animal refuse, but in 
the aggregate the danger from this source is small. 


* Hueppe, Prin. of Bact., English trans., p. 193. 



DISEASES TRANSMISSIBLE BY WATER . 


i /5 


INFECTIOUS DISEASES TRANSMISSIBLE BY WATER-SUPPLIES. 

202. Conditions Necessary for Infection.—The danger of a water- 
supply serving as a vehicle for the transmission of disease rests (i) 
on the possibility of such organisms finding their way into potable sup¬ 
plies, and (2) on the ability of the bacteria so introduced to grow in 
such waters, or at least retain their vitality for sufficient periods of time 
to permit of infection. 

If, under ordinary conditions, water is not a medium in which a 
pathogenic organism is able to live, then there is practically no danger 
of spreading such disease in this way. On the other hand, if the 
specific microbes are able to grow, or even to live for a considerable 
period, in waters that normally are used as public supplies, and these 
forms are also liable to be introduced into the same, then the danger 
from this source is well worth consideration. 

But even though a disease germ may be able to live in water, it 
does not necessarily follow that danger to human beings exists on 
account of this. Not a few of the disease bacteria that are able to 
retain their vitality in water when placed under experimental conditions 
would not under normal circumstances find their way into supplies. 

203. Water-borne Diseases affect Intestinal Canal.—Only those dis¬ 
eases that are able to establish themselves in the alimentary canal are 
at all likely to be transmitted in this way. This might include those 
that affect the throat, as diphtheria or scarlet fever, but, generally 
speaking, the danger is confined to those diseases that establish them¬ 
selves in the intestines. 

In some cases, as in typhoid fever, a disease can enter only through 
a single organ or kind of tissue, as the intestine in this instance; in 
other cases, as in anthrax or tuberculosis, the specific cause establishes 
itself in the body in several different ways. But it must be kept in 
mind that there are numerous human diseases that do not obtain a foot¬ 
hold in the body through the water that is drunk. These may there¬ 
fore be practically neglected by the sanitary engineer in his work. 

204. The Most Important Water-borne Diseases.—The most impor¬ 
tant diseases to consider in this connection are typhoid fever and 
cholera. These are the distinctively water-borne diseases; and while 
there are others that should be mentioned, yet practically the question 
of pollution with specific disease bacteria is confined to a discussion of 
the relation that these two maladies have to public water-supplies. 
Of these two, in this country under normal conditions, cholera is of 
much less importance, as it is distinctively an Oriental disease, whose 


I ?6 COMMUNICABLE DISEASES AND WATER-SUPPLIES. 


natural home is in India. Now and then, on account of the close 
intercommunication between Europe and the Orient, and the laxity at 
times of quarantine regulations, cholera breaks over its natural bound¬ 
aries and devastates regions widely remote from its native home. 
Here in America the danger from the disease is much lessened, unless 
a widespread epidemic should break out in Europe. 

Typhoid fever, on the other hand, is a disease that is naturally 
endemic to America as well as other countries, i.e., it occurs contin¬ 
ually with more or less regularity. Neither of these two diseases is 
contagious in the strict sense of that term, i.e., contracted by mere 
contact with an affected individual. The germ causing the same does 
not travel of itself through the air as in the case of smallpox or scarlet 
fever, but it must be introduced into the susceptible organ, the intes¬ 
tine, through the medium of either the water which is drunk or the food 
which is eaten. That these diseases play such an important role in 
human affairs is a striking commentary on our hygienic methods of the 
present day. In caste-ridden India, where civilization has hardly yet 
emerged from the murky darkness of superstition, perhaps it is excus¬ 
able that cholera should remain endemic; but among the civilized 
nations of Europe and America it is indeed humiliating to admit that 
such an easily preventable disease as typhoid fever is so thoroughly 
entrenched. 

In addition to these two principal diseases that are very easily spread 
by means of polluted water, dysentery and diarrhoeic disturbances 
should also be mentioned as traceable to a similar origin; but these 
troubles are often so imperfectly defined that they are not with certainty 
associated with any definite specific organism. 

205. Typhoid Fever.—This disease is essentially an intestinal dis¬ 
ease, the organism of which finds in the small intestine, especially in 
the lymph-glands of this organ, the most favorable location for develop¬ 
ment. The disease organism, Bacillus typhosus , multiplies rapidly in 
the intestine, and is evacuated in the dejecta and sometimes in the urine 
as well A Carelessness in the disposition of these discharges may result 
in surface-waters becoming polluted with the same. This danger from 
feces has long been known, but it is only recently that the danger from 
infected urine has been thoroughly appreciated. Well-waters, particu¬ 
larly those that are from open and relatively shallow wells, are also 
liable to become infected. 

* Gwyn (Johns Hopkins Hosp. Bull., June 1899) states that from 20 to 30 per cent 
of all typhoid cases show this condition. A most serious factor in this connection is 
their persistence for months in such large numbers after convalescence. Petruschkv 
found as high as 170,000,000 typhoid organisms per cubic centimeter in the urine of 
.a patient. 



DISEASES TRANSMISSIBLE BY WATER. 


177 


The disease organism is introduced into the body through the food 
and drink. Most frequently it gains entrance by means of polluted 
water, but quite often milk and solid food may also function as carriers 
of contagion. Even in milk it is often originally introduced from con¬ 
taminated water that may have been used to rinse or wash the milk- 
utensils, as in the very severe Stamford, Conn., outbreak in 1893, 
where 386 cases of the disease developed in a period of a few weeks. 
Nearly all of these were on the route of a single milkman; and it was 
further shown that infection of the milk was caused by rinsing out the 
cans with cold water from an infected well, after they had been well 
scalded. 

Within recent years it has been abundantly demonstrated that dies 
and insects also often function in distributing the disease by infecting 
food. To such a cause and not to polluted water-supplies were largely 
attributable many of the outbreaks in our military camps during the 
Spanish-American war. 

The period of incubation, i.e., the time between infection and the 
appearance of the disease in the affected person, is somewhat variable, 
ranging from nine days to three weeks, the symptoms becoming charac¬ 
teristic in most cases in about two weeks. This long period of incuba¬ 
tion must be taken into consideration in searching for the origin of 
infection. A person acquiring the disease through polluted water 
would therefore not show any evidence of the same for some time, 
and it is on this account easy to overlook the real source of infection. 
Not infrequently sporadic cases may be acquired in other cities and so 
disseminated by travelers (Fig. 26). Then, again, frequently the disease 
is rather light in character, so that the affected person is not confined 
to the house. The disease is often spread unwittingly by these “ ambu¬ 
lating ” or “walking ” typhoid cases. 

By many it is believed that putrid or offensive gases emanating 
from sewage or any other foul source predisposes the system to this 
disease. On the basis of this belief it is generally regarded that 
sewer-gas is very dangerous. Some experimental results obtained by 
Alessi* seem to indicate that such a view might be true, but this is 
contradicted by Abbott, + whose experimental investigations seem to 
indicate that such gases do not affect the health of animals, The 
mortality of laborers in the sewer systems of large cities or in con¬ 
nection with sewage-disposal plants does not sustain the view that 
inhalation of air over sewage is especially dangerous. 

* Cent. f. Bakt., 1894, XV. p. 228. 

f Trans, of Cong, of Amer. Phys. and Sur., 1894, pp. 28-55. 




178 COMMUNICABLE DISEASES AND WATER-SUPPLiES. 

The mortality-rate in typhoid fever varies considerably in different 
outbreaks, ranging from a few to over 20 per cent, and averaging on 
the whole about 10 per cent of the case-rate. 

Although the disease at present is much more wide-spread than 
necessary (owing to our failure to regard hygienic measures that would 
limit its distribution), still it is diminishing rapidly in amount as is indi¬ 
cated by the data compiled from the Massachusetts vital statistics. 

TABLE NO. 29 . 


DECREASE IN TYPHOID FEVER IN MASSACHUSETTS FROM 1871-1897. 



Typhoid Death Rate 

Percentage of Typhoid 


per 10,000 Population. 

Deaths to Total Mortality. 

1871-1875 

8.2 'j 


1876-1880 

4.6 I 


1881-1885 

5-0 ( 

2.7 

1886-1890 

4.16 J 


1891-1895 

3-25 

1.62 

1896 

2.77 

I.46 

1897 

2.37 

I.42 

In the five large cities 

in the United 

States the percentage of 

typhoid deaths to total mortality has ranged 

as follows from 1870-95, 

inclusive: 

TABLE NO. 30 . 


PERCENTAGE OF TYPHOID DEATHS 

TO TOTAL MORTALITY IN FIVE AMERICAN CITIES. 

• 

Average 
for 25 yrs 

Lowest. Highest. 

New York. 


0.7 1.8 

Brooklyn. 


0.6 I.I 

Boston. 


1.2 3.0 

Philadelphia. 


1.4 4-0 

Chicago. 


I.08 7.2 


206. Typhoid Fever and Sewage Pollution.—The history of almost 
every large city has been that with the growth in population and con¬ 
sequent increase in sewage the amount of typhoid fever has steadily 
increased. This is particularly striking in those cities that are situated 
on river systems or large bodies of water where surface-waters serve 
the dual purpose of public water-supply and sewage disposal. 

On river systems, particularly in the more thickly populated regions 
of this country and Europe, cities frequently draw their public supplies 
from running streams that may have been polluted by the sewage of 
towns above them. With the natural growth in population the zone 
of pollution in the stream is constantly widening, and hence supplies 
from rivers which at one period might have been satisfactory are con¬ 
tinually being endangered. 







DI SEA SES TEA NSMISSIBLE BY WA TER. 


1 79 


The increase in typhoid fever in such cases is generally gradual, 
but at intervals an especially severe outbreak in any one town will 
often be reflected in other outbreaks in towns situated lower down the 
river. This synchronous development of the disease proves the fact 
beyond dispute that the rise and fall of typhoid is often closely related 
to pollution of municipal supplies from sewage. 

207, Mohawk Valley Epidemic,—A most instructive case of this 
simultaneous development of disease due to sewage pollution is seen 



Fig. 25.—Distribution of Typhoid Fever in Mohawk-Hudson Valley. 

(Adapted from Mason.) 

Typhoid epidemics shaded (relative intensity of outbreak denoted by shading). 

in the series of typhoid epidemics that occurred in the towns in the 
valley of the Mohawk and Hudson rivers in 1890-91. 

In July, 1890, typhoid became epidemic in Schenectady and con¬ 
tinued until April, 1891. Seventeen miles down the Mohawk is 
Cohoes, a city of about 22,000. Typhoid broke out here in October, 
1890, and before April, 1891, there had been 1000 cases. The disease 
was exceptionally mild; but notwithstanding this the typhoid death- 
rate for the period of the epidemic was equal to an annual death-rate 
of 45 per 10,000 inhabitants, or about 12-15 times the normal. 

West Troy, taking its supply also from the Mohawk above Cohoes 
(see map), suffered from an epidemic from November, 1890, till 
February, 1891, except for a brief period when the supply of the village 

















i8o 


COMMUNICABLE DISEASES AND WATER-SUPPLIES. 


of Green Island was used. Six miles below West Troy is Albany. 
Here again the disease became epidemic in December, lasting through 
the spring. Waterford, Lansingburgh, and Troy took their supply 
from other sources than the Mohawk, or the Hudson below the junction 
with the former stream. So far as this outbreak was concerned they 
escaped entirely. 

The progressive development of the disease in all of those towns 
that used water from the Mohawk, and its absence in other towns 
situated on the Hudson that were supplied from other sources, shows 
conclusively the influence which the sewage pollution of Schenectady 
and other upper towns had on the distribution of the disease. 

208. Lowell-Lawrence Epidemic. —A similar development was also 
noted in the case of the towns of Lowell and Lawrence on the Merrimack 
River in Massachusetts. In 1890-91 an especially severe outbreak of 
typhoid occurred in Low r ell which was traced to the water-supply. 
The source of supply was the river-water, and Sedgwick showed that 
the probable origin of the polluted condition was attributable to several 
cases of the disease at North Chelmsford, a small village situated three 
miles above, on a tributary of the Merrimack. These cases occurred 
in August, September, and October. 

The sewage of Lowell empties into the Merrimack, and after 8 hours’ 
flow the river-water is utilized by the city of Lawrence, 9 miles below. 
Water polluted by the sewage of Lowell might thus reach Lawrence 
the same day. It would take several days (7-10) to pass through the 
supply-reservoir before it found its way into the service-pipes. From 
an inspection of Table 31 the direct relation between the outbreak in 
Lawrence and the polluted river-water derived from Lowrell is evident. 


TABLE NO. 31 . 


RELATION OF TYPHOID OUTBREAK IN LOWELL AND LAWRENCE. 


Deaths from Typhoid in 
September, 1890., 
October “ .. 

November “ .. 

December “ .. 

January, 1891.... 
February “ ... 
March “ .... 


Lowell. Lawrence. 


8 

3 

10 

3 

28 

7 

26 

>9 

19 

19 

14 

11 

IO 

6 


209. Pollution of Lake Towns. —Pollution of water-supplies from* 
sewage is not confined to river towns. Cities situated on lakes, even 
on our Great Lakes, frequently suffer from contamination of their sup¬ 
plies through disposing of their sewage in the same way. This is 









DISEASES TRANSMISSIBLE BY WATER. 1 8 1 

noted in a striking manner in the case of Chicago, which takes its 
supply from Lake Michigan. Although a portion of its sewage has 
been pumped for a number of years into the old Illinois and Michigan 
Canal, still the pollution of the lake-water has been constantly increas¬ 
ing through the drainage of the Chicago River and also the numerous 
sewer-outfalls that empty directly into the lake. Through the custom 
of emptying into the lake the dredge-dumpings from the river, the 
water-supply has also been grossly polluted at times and has caused 
epidemics of typhoid.* 

The earliest water-intakes were located only a short distance from 
shore. These have been gradually extended into the lake from i to 2 
miles, but the endemic condition of typhoid fever in the city and the 
enormous increase in 1891 led to the extension of the main tunnel to 
4 miles in 1892, after which the amount of typhoid rapidly decreased,, 
as shown in the following figures: 

TABLE NO. 32 . 

TYPHOID DEATH-RATES IN CHICAGO PER 10,000 POPULATION BEFORE AND AFTER THE 

FOUR-MILE EXTENSION OF THE WATER-INTAKE. 


’86 

'87 

’88 

'89 

’90 

’ 9 i 

’92 

Av. 7 yrs. 

6.8 

5 -o 

4*7 

4.8 

8.3 

16 

10.4 

8.0 

*93 

’94 

'95 

’96 

’97 

'98 

'99 

Av. 7 yrs. 

4.2 

3 -t 

3-2 

4.6 

2.7 

3-8 

2.5 

34 

Even the 

relative 

immunity obtained by the 

four-mile 

tunnel was 


not of long duration, for in a few years it was not uncommon to find at 
times that the water was polluted. A heavy rainfall that would flush 
out the river would frequently pollute the lake out to the four-mile in¬ 
take. With the inauguration of the Drainage Canal in 1900, by which 
tb? entire sewage is diverted from the lake, it is confidently expected 
that the water-supply will be improved, a condition which will un¬ 
doubtedly reflect itself at once in the lessened death-rate of this disease, t 
210. Typhoid and Polluted Wells.— Although the larger epidemics 
of typhoid fever are necessarily connected with impure municipal water- 
supplies, still it also frequently happens that polluted wells are the 
means of distributing the virus of the disease. The opportunity for 


* Bull, of Chicago Health Dept., Aug. 1899 

f The diminution in percentage of typhoid deaths for the first six months of 1900 
is very marked. There were 123 deaths from typhoid for the first half of 1900, in 
comparison with an average of 203 for a similar period of the years 1897 to 1899 

inclusive. 




182 


COMMUNICABLE DISEASES AND WATER-SUPPLIES. 


infection is considerably greater in the case of private or public wells, 
but the spread of the disease is likely to be more restricted because of 
the smaller number of users; but on the whole the aggregate of typhoid 
cases that are infected in this way frequently exceeds that caused by 
polluted general supplies. It often happens that persons acquire the 
disease in other towns than where the disease first becomes manifest 
(see Fig. 26), but, excluding this, by far the larger amount of typhoid 
fever incident to polluted water that occurs in other than urban popu- 



Fig. 26.— Movements of Contagium of Typhoid Fever. (Mich. Board of Health.) 

Direction of arrows indicates movement of disease and shows how new foci are 
established by importing cases from without. 

lations must come from infected wells. Even in cities a considerable- 
proportion of this disease is attributed to the use of old wells. This is 
particularly the case in the more congested poorer quarters, where these 
older sources of supply are retained much longer than in the newer and 
better built portions of towns. In 1889 ' m Washington 626 fatal cases 
of typhoid occurred in families using water from about 300 different 
wells, a sanitary record for our capital city that is indeed humiliating. 

The general decline in typhoid death-rates in cities coincides in a 
remarkable way with the introduction of public water-supplies, as has 
been noted especially in Massachusetts (Fig. 27).* 

* 28 Rept. Mass. Bd. Health, 1896, p. 781. 











DISEASES TRANSMISSIBLE BY WATER. 183 

211. Outbreaks Inaugurated from Single Cases.—While the con¬ 
tamination of municipal water-supplies is generally due to municipal 
sewage pollution, still it may at times happen that a single case of 
disease may be the means of inaugurating an outbreak, as in the 
Plymouth, Pa., case. This epidemic, consisting of over 1100 cases in 
a town of 8000 people, had its origin through the pollution of the 



/ 356-6S 7366-75 7376-35 7336-35 

Oeotfy Rate from TypT)o/a7 Perer per 700,000 - 

Per cert of Popu/ation not <supp77ec7Tr/t/r PuI7/c Wafer - 

Fig. 27. —Decrease in Typhoid Death-rates Coincident with Introduction 

of Public Water-supplies. (Mass.) 

impounded drinking-water by the fecal discharges of a single patient. 
To prevent infection of the family vault, the dejecta were deposited on 
the surface of the snow. Soon after, heavy rains washed the frozen 
hillsides, the natural surface-drainage discharging into the stream that 
fed the supply-reservoir. Within about two to three weeks a very pro¬ 
nounced epidemic occurred that was confined closely to the patrons of 
the municipal water-supply. 

212. Typhoid Rates an Index of Quality of Water.—A study of the 
death-rate or case-rate of typhoid fever in various towns and cities for 
a number of years illustrates in a striking way the relation that exists 
between this disease and the general character of the public water- 
supply. To some extent, typhoid may be introduced into a city from 
an external source (Fig. 26). This factor is generally more important 
in the smaller towns in which the transient population is relatively large, 
as in mining and lumbering regions. In some degree, the disease may 
also be traced to other causes than impure water, but by far the larger 
majority of cases are attributable to infection of this character. Cities 
deriving their supply from sources in which the probability of pollution 
is excluded have as a rule a very low typhoid death-rate; those, on the 
other hand, using surface-waters (impounded or streams) generally 
show an increase in this rate. Hill * has classified cities on the basis 


* Public Water-supplies, p. 70. 













184 COMMUNICABLE DISEASES AND WATER-SUPPLIES. 


of their death-rates from this disease into seven groups, beginning with 
those having a typhoid death-rate of ten or less per 100,000 popula¬ 
tion, and increasing each group by 10. The seventh class embraces 
all cities whose typhoid death-rate exceeds 60 per 100,000. It is a 
significant fact that reflects upon our sanitary methods in this country 
to observe that there is no American city in Class I or II with the 
exception of New York and Brooklyn. Hill has even suggested that 



S 6 7 6 S <1 J a / 0 10 PO 30 10 JO 60 70 60 SO 



Fig. 28.— Relation of Typhoid Death-rate to Character of Water-supply 
in European and American Cities ; also Population supplied from Each 
Source. (Fuertes.) 

contracts for supplies should be made on the basis of a certain death- 
rate from typhoid, but to determine the effect of any given improvement 
like this requires the collection of data for several years, and would 
therefore seem impracticable for this purpose. 

Fuertes * arranges these statistical data on the basis of the kind of 
water furnished each municipality, as mountain spring, filtered water, 
ground-water, surface-water (streams, impounded waters, and lakes). 
In Fig. 28 the limits between which 75 per cent of the death-rates per 
100,000 may be expected are shown for the different kinds of waters 
used; also the population using each class. Of the total population as 


* Water and Public Health, p. 32. 

























































































DISEASES TRANSMISSIBLE BY WATER . 


185 


charted (over 33,000,000), 20,000,000 are in European cities, the 
remainder in America. Over 75 per cent of the total European popu¬ 
lation here represented have a better supply than an impounded reser¬ 
voir, like the Croton supply of New York, while over 75 per cent of 
the supplies furnished American cities are below this standard. 

213. Diminished Typhoid Rates Incident to Improved Supplies.— 
From the typhoid death-rates it is very evident that the water-supplies 
of European cities are much better than those in America. This con¬ 
dition, however, has not always obtained, as in most cases European 
municipalities have had to pay the penalty of impure water by high 
death-rates before their supplies were bettered. The much denser 
population per square mile in Europe increases of course the amount 
of pollution in most surface-waters, and makes it thereby increasingly 
difficult for large cities to secure adequate supplies that are beyond the 
taint of suspicion. In mountainous regions pure natural waters can 
frequently be obtained, but in the cities situated on the seacoast and in 
the plains region sufficient natural supplies of pure surface-water are 
to be had only in exceptional instances. This has led to the purifica¬ 
tion of waters taken from available sources of supply. The diminished 
typhoid death-rates under these conditions, as compared with those that 
obtained before such improvements were made, indicate in the most 
conclusive manner the close relation that exists between the quality of 
water-supplies and public health, so far as water-borne diseases are 
concerned. These diminished typhoid death-rates, however, have not 
been gained entirely by securing an unpolluted or a purified water- 
supply, but in part through the introduction of improved systems of 
sewerage. 

In Zurich the introduction in 1885 of new filters carefully controlled 
caused the following marked decrease in typhoid rates per ioo,ooq 
population: 

TABLE NO. 33 . 


TYPHOID DEATH-RATES IN ZURICH, SWITZERLAND, PER 100,000 POPULATION, IN 
RELATION TO IMPROVEMENTS IN WATER-SUPPLIES. 


*79 

33 


Before Improvement. 

’8o ’81 ’82 ’83 ’84 

80 43 48 27 174 


Av. 7 yrs. 

’85 

no 73.6 


’88 

8 


After Improvement. 


’8g ’go 
g 10 


’92 

8-5 


*93 

7-5 


Av. 9 yrs. 


’86 

10 


’87 

13 


’ 9 i 

8 


’94 

7 


9.0 


1 86 COMMUNICABLE DISEASES AND WATER-SUPPLIES. 

In the case of Munich the diminution in typhoid losses was coinci¬ 
dent with the installation of the sewerage system, although the water- 
supply was not changed until several years afterward. 

Fig. 29 shows the pronounced drop in the typhoid rate and the 
relation of the same to sewerage introduction. 



Fig. 29. —Typhoid Death-rate in Munich ; Relation of Same to Introduction 

of Sewerage and Water-supply. (Fuertes.) 

214. Seasonal Distribution of Typhoid Fever.—Typhoid fever does 
not rage with equal severity throughout the entire year. Usually the 

case-rate increases in late summer and 
fall, often reaching a maximum during 
the winter and then declining in the 
spring months. Fig. 30 indicates this 
unequal distribution. Of course during 
outbreaks of this disease this general rule 
does not obtain, as infection may rapidly 
pass from one person to another. Wood- 
head* attributes this higher case-rate in the 
fall to the higher temperature of the water, 
facilitating the growth of the typhoid 
organism, but this point is by no means 
thoroughly established. The ability of 
the organism to retain its vitality when frozen, even though it is not a 



* Roy. Com. on Met. Water-supply, 1893, p. 506. 


























































DISEASES TRANSMISSIBLE BY WATER. 1 87 

spore-producing germ (184, 223), shows how the disease may be 
spread even in winter. 

215. Asiatic Cholera.—While cholera is a disease that is naturally 
“at home” in the Orient, particularly in India in the delta of the 
Ganges, still ever and anon it breaks over the boundaries that naturally 
limit it and becomes epidemic among western nations. Europe has 
been visited with this disease a number of times during the last century, 
the last outbreak occurring in Germany in 1892-3. _It has less fre¬ 
quently invaded this country, although eight epidemics are recorded 
since 1832. The epidemic of that year and those of 1853-54 and 
1873 were the most severe. Since the latter date, the disease has not 
occurred in this country. 

Like typhoid fever it is primarily an intestinal disease, the organism 
associated with it developing luxuriantly in the intestine and therefore 
occurring in large numbers in the dejecta of cholera patients. This 
causative organism was discovered by Koch in 1884 in India, where he 
succeeded in isolating it from the intestinal contents of cholera patients; 
also finding the same in water from an open uncovered drinking-tank. 

216. Cholera Outbreaks traced to Water-supplies.—In 1854 London 
was visited with a severe epidemic. The cholera death-rate in that 
portion of the city supplied by one company that drew its supply from 
the polluted Thames was 154 per 10,000, while in another quarter fed 
with an unpolluted supply there were only 17 deaths per 10,000. 

The 1892-93 outbreak in Europe gave ample opportunity for the 
study of the disease in the light of modern methods. Although the 
specific organism had been found before in several cases associated with 
epidemics of the disease, many new data were gathered at this time and 
the relation of the cholera organism to water-supplies thoroughly con¬ 
firmed by bacteriological examinations. In these studies it was also 
found that surface-waters not infrequently contain other bacteria of the 
spirillum type. Many of these closely simulate the cholera or comma 
organism, as it is sometimes called on account of its shape, but 
Pfeiffer’s test and certain cultural methods permit of a ready differentia¬ 
tion (149). 

The most striking illustration of the way in which the disease is 
spread by water-supplies is shown in the Hamburg outbreak. Ham¬ 
burg, a city containing at that time a population of 640,000, and 
Altona, a city of 150,000 people, are situated on the River Elbe near 
its mouth. The two cities are practically one, a| they merge into each 
other, although they have a separate city government. Hamburg 
at this time drew its water-supply from the Elbe some distance above 


1 88 COMMUNICABLE DISEASES AND WATER-SUPPLIES. 

the city. Altona, situated just below and forced also to use the Elbe 
water, took it at a point 8 miles down-stream, treating it by sand filtra¬ 
tion because of its impure condition. Hamburg therefore received 
unfiltered Elbe water, subject of course to possible pollution; Altona 
used filtered river-water, taken from the stream after it had received the 
sewage of over 800,000 people. Cholera broke out in the fall of 1892, 
and during this epidemic there were 17,000 cases (16,800 in less than 
two months) in Hamburg with over 8600 deaths, while during the 
same time there were only about 500 cases with about 300 deaths in 
Altona. Hamburg with its unfiltered river-supply had a case-rate of 
about 263 per 10,000 and a death-rate of 134, while in Altona the 



Fig. 31. Hamburg-Altona Epidemic of Cholera in 1892. 

Deaths from cholera are shown in district 400 meters each side of Hamburg-Altona 
boundary. Section in Hamburg marked C was supplied with Altona water and 
wholly escaped the disease. 

ease-rate was 38.1 and the death-rate 21.3. Of the number in the 
latter city it must be remembered that the disease was contracted in 
many cases by people who worked in Hamburg but lived in Altona. 
One block of buildings in Hamburg, containing about 400 people, re¬ 
ceived its water-supply from Altona rather than Hamburg on account 









DISEASES TRANSMISSIBLE BY WATER. 


189 


of local difficulties in connecting- the main. This spot (C on map), 
although surrounded with cholera cases, remained free from the disease. 
Several of the large hospitals, garrisons, and prisons in Hamburg that 
used other water than the municipal supply escaped with little or no 
disease. The history of the epidemic shows in the most conclusive 
manner that the river-water was the means by which the disease was 
spread. In fact, the cholera spirillum was isolated not only from water 
taken from the Elbe, but also in one of the Altona filter-basins before 
the water was submitted to filtration.* 

217. Anthrax.—This disease is not often disseminated by means of 
the drinking-water, but waters of surface origin may receive drainage 
from fields on which the disease may be present, and so become con¬ 
taminated. This condition is especially liable to occur in those regions 
(Europe, Asia, and Africa) where the disease is severe. Here in this 
country it is not established except in a few localities (Lower Missis¬ 
sippi valley, Lower Delaware River, etc.). 

Rivers are more apt to be the distributive agents so far as waters 
are concerned. On account of using hides and skins imported from 
infected regions refuse from tanneries, brush-factories, and morocco- 
shops disposed of in running streams may often be the cause of out¬ 
breaks along watercourses. 

A striking instance came under the writer’s attention in 1899. The 
Black River, for a distance of 10 miles below Medford, Wis., was pol¬ 
luted by tannery refuse. Stock (cattle and horses) contracted anthrax 
by drinking the river-water, by grazing on lowlands that had been 
subjected to overflow in the spring, and by eating hay that had been 
gathered from the inundated marshes. I11 caring for the affected stock 
several persons also became infected. The disease germ was introduced 
from a tannery in which Chinese hides were being handled. 

Diatroptoff t notes the detection of the specific organism in the case 
of a well-water. The water from this well served to infect a herd of 
sheep. The writer in the Medford outbreak succeeded in isolating the 
disease organism from a pond that had become infected by surface 
drainage from fields on which cattle had died from anthrax. 

218, Other Water-borne Diseases.—In addition to the above, a con¬ 
siderable number of other diseases are also distributed more or less fre¬ 
quently by the aid of water. In some cases the causal organism that 
produces the disease is not yet known, but the manner in which the 
outbreak is disseminated leaves no room for doubt as to the probability 
of water functioning in its spread. The winter outbreaks of cholera 


* Zeit. f. Hyg., xiv. p. 337. 


f Ann. Past., 1893, VII. p. 286. 








I90 COMMUNICABLE DISEASES AND WATER-SUPPLIES. 

infantum that have occurred in Hamburg and Altona have been traced 
directly to the use of raw or imperfectly filtered Elbe water." 

219. Gastro-intestinal Disturbances.—As representing this class of 
diseases may be mentioned gastro-intestinal catarrhs. In some cases 
a diarrhceic condition may be produced as the result of the presence of 
suspended matter. In a number of instances, epidemics of intestinal 
catarrhs have been associated with the pollution of waters with organic 
matter from various sources. The Long Branch,t N. J., outbreak was 
ascribed to the use of peaty water, but it was not definitely shown 
whether the disturbance was due to the organic matter of peaty origin 
or to organisms that were present in such water. 

Wright X instances an outbreak in Buffalo that was confined entirely 
to persons who used water from a series of shallow wells in a certain 
region of the city. 

Cameron § records an epidemic in a military school in Dublin where 
150 persons were afflicted. The trouble was traced to a ground-water 
that was found to be rich in micro-organisms. 

In 1894 a very extensive outbreak of an enteric disease appeared 
in Lisbon, || Portugal. In three months over 15,000 people were 
afflicted. The symptoms of the disease appeared like cholera in many 
ways, but the fact that only one person died from the same indicated 
at least that the germ in its pathogenic properties was much different 
from true Asiatic cholera. The organism producing the outbreak was 
readily separated from fecal discharges of affected persons, and was also 
found in the water-supply of the city. It bore a striking resemblance 
to the comma bacillus of cholera. The protection afforded by the use 
of household filters demonstrated conclusively that the disease was dis¬ 
tributed by the way of the water-mains. 

220. Dysentery,—Although it is quite probable that dysentery may 
be caused by more than one kind of organism, the relation of diseases 
of this class to polluted waters is now quite generally accepted. The 
severe form of the disease that occurs in the tropics is ascribed to the 
development of an animal parasite, Amoeba coli, while the disease as it 
appears in some other countries seems to be associated with certain 
bacteria. As these organisms have not been definitely determined in 
water-supplies, the supposed connection between them and water does 
not rest upon a thoroughly established scientific basis, but is based 
upon the distribution of the disease and other epidemiological data. 


* Hazen. Filtration of Public Water-supplies, p. 228. 
f Mason. Water-supply, p. II. \ Sanitary Record, iv. p. 185. 

§ Dublin Jour. Med. Sc., 1. p. 535. || Cent. f. Bakt., 1894, xvi. p. 401. 




VITALITY OF PATHOGENIC BACTERIA IN WATER. 191 

221. Malaria.—Regarding the spread of malaria by means of water- 
supplies, not much definite information that is scientifically established is 
at hand, although the general belief has been that the disease is sometimes 
spread in this way. The recent establishment of the mosquito theory 
of infection shows, however, that water is necessary for the continuance 
of the disease, although possibly the introduction of the malarial para¬ 
site does not occur through the water that is ingested, even though 
such water might contain the larvae of the spotted-wing mosquito ( Ano¬ 
pheles ) that is now known to be the means of distributing the disease. 

VITALITY OF PATHOGENIC BACTERIA IN WATER. 

222. Conditions Affecting Vitality,—While common experience has 
for centuries associated certain diseases with impure or polluted water- 
supplies, it has not been possible until the methods of bacterial inves¬ 
tigation were employed to determine just how long a water once 
rendered impure through fecal or other pollution would remain 
dangerous to human health. Since the discovery of the specific 
organisms that are the inciting cause of different diseases, and the study 
of them under varying conditions in waters of diverse sources, as to 
how long such organisms are able to retain their vitality in natural 
waters, it has become possible to limit much more accurately this 
period of danger. 

It is very important to recognize: 

(1) Whether pathogenic bacteria once introduced into water are 
able to multiply therein; and, 

(2) Supposing that conditions do not favor their growth, how long 
such pathogenic bacteria are able to retain their vitality and virulence. 

Having once determined these conditions, it then becomes possible 
to state with some degree of accuracy the period during which water 
polluted with such germ-life is dangerous. 

Any satisfactory answer to these propositions must take into con¬ 
sideration a number of conditions, both as to the organism and the 
influence of its environment, that will exert a varying effect on the 
vitality of any germ. The more prominent of these factors are as 
follows: 

Natural variation in the organism itself, due to age, condition of 
culture, and previous history of the same; the number of disease germs 
present in the water; the condition of the water as a growth medium 
as to its composition, the amount of organic matter, the nature of the 
same, whether it is suspended or soluble, the presence of by-products 


192 COMMUNICABLE DISEASES AND WATER-SUPPLIES. 

, of previous bacterial growth, the chemical reaction of the water itself; 
the effect of varying conditions in environment as to the temperature 
of the water, the amount of oxygen dissolved, the effect of light, and 
the state of water as to motion. 

All of these factors exert more or less effect on the vitality of 
bacteria, and particularly on that of disease-producing microbes. In¬ 
asmuch as these conditions are not constant in all waters, it naturally 
follows that any specific organism will be subject to a good deal of varia¬ 
tion in the length of time it will remain in a living condition in water. 
It is therefore not so surprising to find considerable difference in experi¬ 
mental results, which fact should lead to caution in deducing definite 
laws as to this question. 

223, Vitality of Typhoid Organism,—The closer relation of typhoid 
fever to polluted water-supplies renders a determination of the vitality 
of this germ of more than ordinary importance. Although the typhoid- 
fever . bacillus is not a spore-bearing form, nevertheless it is able to 
retain its vitality in drinking-waters for a considerable period of time, 
as is evidenced by the numerous outbreaks traceable to infected 
supplies. 

Under ordinary conditions, from the direct experiments already 
made, it seems improbable that there is any considerable growth of the 
typhoid bacillus in potable waters, although, as Frankland * has shown, 
it is possible to acclimate the organism to such a dilute food-medium 
that it will actually grow in surface-waters; but under the circumstances 
in which it would naturally find its way into potable supplies there 
would be but scant opportunity for this acclimation process to occur. 
Where organic matter is present that is available as a food-supply, as 
in sewage-polluted waters, cell-multiplication may be possible, + but 
even here there are other retarding factors, such as the effect of 
bacterial by-products, that tend to prevent growth. 

In order to determine the period through which the organism is 
able to survive in water, a large amount of data has been collected. 
The results, however, are so conflicting that it is impossible to closely 
define these limits. Frankland’s work J on the whole seems to be the 
most closely controlled. He experimented under summer conditions 
with a hard, somewhat polluted surface-water (Thames), a soft, peaty 
water (Loch Katrine), and a hard, deep well-water. Three series of 
tests were made from each source, in raw water, the same after sterili- 

* Zeit. /. Hyg ., 1895, XIX. p. 406. 

f Olivier. Comp. rend. d. sc. Soc. de Biol., 1889, No. 27. 

\ l.c., p. 402. 





VITALITY OF PATHOGENIC BACTERIA IN WATER. 


l 9 3 


zation by steam, and also after being rendered germ-free by filtration. 
The results are as follows: 

VITALITY OF B. TYPHOSUS IN DIFFERENT WATERS (FRANKLAND). 

Period in Days when Typhoid Organism was last found. 


Raw. 

Thames. 

Katrii'e. °“P Well. 
*9 33 

C T nr\ 

Steam sterilized. 


Filtered. 


0 A JO 

39 11 


The tests made on the waters sterilized by heat and by filtration 
are of course not applicable to normal conditions, but they are ol 
interest as showing the influence of competition with other bacteria. 
If the number of typhoid organisms added was small, they disappeared 
somewhat more rapidly. 

Other observers have obtained results quite different from these, but 
in many instances the conditions surrounding the test were so artificial 
as to render the data collected of little value. 

From a comparison of all available data, it seems quite evident that 
this organism is able to retain its vitality in potable waters for at least 
several weeks.* * * § 

Under normal conditions the typhoid organism generally finds its 
way into waters through the medium of sewage, and it is of the utmost 
importance to know just what effect the addition of organic matter of 
this character would exert on the vitality of the organism in such 
waters. 

Frankland found that in surface-waters, although containing more 
organic matter, the typhoid bacillus disappeared more rapidly than in 
unpolluted well-waters. Klein + reports similar results, while in the 
experiments of Kraus X the organism was killed in pure spring-water 
in five days, although it lived in raw Thames water for five weeks. In 
observations made directly on typhoid feces, Karlinski§ found that the 
organism was generally demonstrable for a period of two to three 
weeks. 

The evidence is practically unanimous that this organism persists 
Jonger in cold waters than in those of summer temperature. At 
Lawrence the rate of decrease was noted as follows when the typhoid 


* Kruse. Zeit. f. Hyg ., 1894, xvn. p. 43, 

f Rept. Loc. Govt. Bd. (Great Britain), 1894-5. 

% Arch. f. Hyg.. 1887, VI. p. 251. 

§ Cent. f. Bakt ., 1889, VI. p. 65. 






194 COMMUNICABLE DISEASES AND WATER-SUPPLIES . 


bacillus was exposed in Merrimack River water kept near the freezing 


point. 

Day of analysis. i 5 10 15 20 25 

Number per c.c. 6120 3100 490 100 17 o 


The spread of the disease from Lowell to Lawrence during the 
winter, and the Plymouth, Pa., case in which typhoid dejecta were 
exposed in the snow from January to March to a minimum tempera¬ 
ture of — 22° F., indicate that low temperatures are certainly ineffective 
agents in the destruction of this organism. 

224. Cholera.—In the experimental results obtained as to the 
vitality of the cholera spirillum in natural waters, the data are even 
more conflicting than with typhoid. In order to encourage growth, 
Bolton * found that about 400 parts of organic matter per 1,000,000 were 
necessary. This explains why the germ lives longer in a polluted than 
in a pure water. Trenkmann t has determined that the vitality of the 
cholera spirillum is considerably prolonged where the organism is 
grown in solutions containing sodium chloride. This is of interest 
as explaining the presence of the organism in brackish waters (river 
Elbe at Hamburg,'! harbor at Marseilles). 

In general, the experimental results indicate that the cholera'spiril¬ 
lum is unable to retain its vitality in potable waters for as long a time 
as the typhoid bacillus. In the majority of experiments cited, the 
duration of vitality was only 1-3 days. On the other hand, some 
reputable observers claim to have found it in ordinary water several 
months after infection. In Cologne sewage Stutzer and Burri § found 
it lived from /—13 days. 

At low temperatures it retains its ability to grow, as has been 
determined experimentally, as well as empirically in the winter 
epidemics that occurred at Nietleben and Altona in 1893.ll 

Owing to the fact that the period of incubation with this disease is 
quite short (1-5 days), it is more often possible to detect the presence 
of this organism in polluted supplies than it is with typhoid. (See 
Literature of this chapter.) For such determinations the differential 
media that have been devised may be successfully used (149). 

225. Anthrax.—The problems presented in the case of this disease 
organism differ materially from those previously noted, in that Bacillus 

* Zeit. f. Hyg ., I. p. 1. 

f Cent./. Bakt. t 1893, XIII. p. 313. 

% The chlorine content of river is greatly increased by the waste waters from the 
Stassfurt salt-works (See Aufrecht, Cent. f. Bakt., 1S93, xm. p. 353.) 

£ Hyg. Rund., iv. p. 208. 

| Koch. Zeit. f. Hyg., 1893, xiv. p. 393. 






CON CL USION. 


195 


anthracis is able to form spores, and hence is much more resistant. 
Spores, however, are only produced in contact with air and where the 
temperature is at least 6o° F. 

There is little probability of the pollution of waters by anthrax from 
human sources, but it not infrequently happens that this disease organism 
finds its way into water from animal sources, and inasmuch as the same 
germ is able to produce anthrax in both man and animals, the origin 
of the same is a matter of no little moment. Tanneries, brush- 
factories, etc., are particularly liable to distribute the disease germ by 
the way of the water, owing to the fact that hides, hair, and wool are 
frequently infected. In such cases the disease germ is more apt to be 
in the spore rather than the vegetative form and therefore will be much 
more resistant. 

In the sporeless stage the organism is able to live but for a short 
time. Two to five days mark the ordinary limits of existence in sur¬ 
face-waters, the organism degenerating more rapidly in summer than 
in winter. Under summer conditions the germ may sporulate, in 
which condition it is able to live over from one year to the next. In 
lowlands subject to overflow, the conditions seem to be the best for the 
perpetuation of the vitality of the organism. 

226, Conclusion.—Experimental tests have been made with other 
kinds of pathogenic bacteria, but the results are only of general scientific 
interest. In summarizing, all bacteria of disease are killed out sooner 
or later in waters. Ordinarily the amount of organic nutriment con¬ 
tained in water is not sufficient to encourage rapid development, and 
the consequence is that most forms are sooner or later starved out. 


LITERATURE. 

A large amount of literature showing the relation of communicable 
diseases to water-supplies is in existence, but for the most part it is widely 
scattered in various hygienic, bacteriological, engineering, and other journals. 
In a few such works, as 

Hill’s Public Water-supplies, 

Fuertes’ Water and Public Health, 

Abbott’s Hygiene of Transmissible Diseases, 
some of the more classic examples are given. The appended list gives some 
of the more striking cases. 


TYPHOID OUTBREAKS. 

Wittenberg , Germany , 1882. Epidemic in garrison, due to infection of 
well from privy over 5° feet distant. 

Gaffky. Mitt. a. d. kais. Gesundheitsamte, 1884, 11. p. 410. 


ig 6 COMMUNICABLE DISEASES AND WATER-SUPPLIES. 


Plymouth, Pa., 1885. One-ninth of entire population of 9000 stricken 
with disease due to pollution of open public reservoir with fecal discharges 
from single typhoid case. 

Philadelphia, Pa., 1897-98. Typhoid epidemic in whole city, but particu¬ 
larly so in sections furnished with water from Queen Lane Reservoir. Water- 
supply drawn from Schuylkill River, infected through overflow of intercepting 
sewer. 

Ann. Rept. Dept. Public Safety of Phila., 1898. 

Lausanne, Switzerland, 1872. Infection of town supply (spring) through 
imperfect filtration of soil. 

Deutsche Arch. f. klin. Med., 1893, Band xi. 

Halle, Germany, Orphanage in, 1871. 

Zuckschwerdt. Public, d. Vereins f. offentl. Gesundheitspflege in Halle, 
No. IV. 

Hamburg-Altona, Germany, 1885-1890 and 1891. 

Wallichs. Deutsche med. Wochenschr., 1891, No. 25. 

Reincke. Der Typhus in Hamburg mit besonderer Beriicksichtigung d. 
Epidemien von 1885-1888. Hamburg, 1890. 

Lowell-Lawrence, Mass., 1892. Infection from Merrimack River dis¬ 
tributed by this stream. 

24 Rept. Mass. Bd. Health, 1892, p. 667. 

Bondville, Provincetown, and Millville, Mass., 1892. Disease disseminated 
by secondary infection from person to person through food-supply. 

24 Rept. Mass. Bd. Health, 1892, p. 732. 

Springfield and Somerville, Mass., 1892. Disseminated by infected milk. 

24 Rept. Mass. Bd. Health, 1892, p. 715. 

Stamford, Conn., 1895. 386 cases developed within six weeks. Of this 

number 97 per cent came from a single milk-supply, the milk being infected 
by rinsing out the cans with cold water from a shallow contaminated well. 

18 Rept. Conn. Bd. Health, 18-95, p. 161. 

Middletown, Conn., 1894. Outbreak produced by diseased oysters infected 
by being “ fattened ” in sewage-polluted waters. 

Conn, H. W. Med. Record, Dec. 15, 1894. 

17 Rept. Conn. Bd. Health, 1894, p. 243. See also 

18 Rept. Conn. Bd. Health, 1895, p. 189. 


CHOLERA OUTBREAKS. 


Hamburg-Altona, Germa?iy, 1892. The most striking case on record of 
the value of sand filters in checking disease outbreaks. 

Koch. Wasserfiltration und Cholera. Zeit. f. Hyg., 1893, xiv. p. 393; 
also ibid. , xv. p. 89. 

Reincke. Ber. d. medic. Inspect, d. Hamburg. Staates f. 1892, p. 28. 
Gaffky. Arb. a. d. kais. Gesundheitsamte, x. pp. 1-129. 

Cholera in Germany other than in Hamburg in 1892—93. 

Arb. a. d. kais. Gesundheitsamte, x. pp. 129-273. 

Korber. Dorpat outbreak. Zeit. f. Hyg., 1895, xix. p. 161. 

Koch. Nietleben outbreak. Zeit. f. Hyg., 1894, xv. p. 123. 

Cholera in Germany in 1894. 

Arb. a. d. kais. Gesundheitsamte, xii. pp. 1-285. 


LIT ERA TURE. 


197 


DIARRHCEAL EPIDEMICS. 

Hamburg-Altona, 1880, 1888, 1892. 

Reincke. Ber. d med. Inspect, d. Hamburg. Staates fur 1892, p. 10. 
Bockendahl. Generalber. ii. d. offentl. Gesundheitswesen fiir Schl. 
Hob, 1870, p. 10. 

(Abstracts of both of these articles in Hazen’s Filt. Pub. Water- 
supplies, p. 226.) 

DETECTION OF PATHOGENIC BACTERIA IN WATER. 

The following list gives a partial bibliography of the instances in which 
the specific disease organisms of typhoid and cholera have been found in 
waters. Owing to the difficulty in differentiating the typhoid-fever organism 
from the colon bacillus, it is doubtless true that in some cases errors have 
arisen through the confusion of these two species. 

Typhoid Fever. 

Moers. Erganzungshefte z. Cent. f. allgem. Gesundheitspflege, 1886, 
11. p. 144. 

Michael. Fort. d. Med., 1886, iv. p. 353. 

Widal. Gazette hebdom., 1886, No. 45. 

Chantemesse and Widal. Rev. d’hyg., 1887, ix. p. 116. 

Beumer. Deutsche med. Wochenschr., 1887, No. 28. 

Thoinot. Sem. medicale, 1887, p. 135. 

Henrijean. Ann. de Microg., 1889, 11. p. 401. 

Jager. Zeit. f. Hyg., 1891, p. 197. 
v. Fodor. Cent. f. Bakt., 1892, xi. p. 121. 

Schild. Zeit. f. Hyg., xvi. p. 373. 

Asiatic Cholera. 

Frankel. Cent. f. Bakt., 1892, xn. p. 914. 

Loeffler. Cent. f. Bakt., xm. p. 380. 

Nicati et Rietsch. Rev. d’Hyg., May 20, 1885. 

Lubarsch. Deutsche med. Wochenschr., 1892, No. 43. 

Koch. Berl. klin. Wochenschr., 1884, p. 239; Zeit. f. Hyg., 1893, xtv. 
PP- 337 ? 406, 417* 

Dunbar. Arb. a. d. kais. Gesundheitsamte, 1894, ix. p. 379. 

Van Ermengen. Sem. med., 1893, p. 272. 

Significance 0/ Bacillus coli communis as an Index 0/ Fecal Pollution . 

Grimbert. Cent. f. Bakt., xvi. p. 506; ibid. xvm. p. 103. 

Smith. Cent. f. Bakt., xvm. p. 494. 

Abbott. Prin. of Bacteriology, 1894, p. 422. 

Klein. 23 Rept. Loc. Govt. Board, Supplement, p. 67. 

Pearmain. Applied Bacteriology, p. 303. 

Kruse. Zeit. f. Hyg., xvn. p. 1. 

Freudenreich. Cent. f. Bakt., xvm. p. 103. 

Rosenau. Quoted in Hill’s Public Water-supplies, p. 28. 


PART II. 

THE CONSTRUCTION OF IV/I TER-WORKS. 


CHAPTER XI. 

GENERALITIES PERTAINING TO WATER-WORKS 

CONSTRUCTION. 

227, In the preceding chapters there have been discussed the 
various matters relating to the requirements of a water-supply and the 
capabilities of the various sources as regards quantity and quality. In 
the remaining portions of this work there will be considered in detail 
the design and construction of the various parts entering into a system 
of water-works. 

Questions of quantity and quality are of prime importance in the 
selection of a source of supply, but that the solution may be the best it 
is also necessary to consider the question of cost, a matter which 
depends upon the extent and character of the various parts of 
the works involved. With two or more sources at hand, each of which 
will furnish water of sufficient quantity and equally good quality, the 
problem resolves itself into one of economy as measured by the first 
cost plus the capitalized cost of operation. The problem is, however, 
rarely so simple as this, questions of future enlargement, differences in 
quality, possible future pollution, and financial resources of the com¬ 
munity being some of the elements which render the question a com¬ 
plicated one. Thus a complete general knowledge of the problem 
becomes a prerequisite to an intelligent selection of source as well as 
to the actual construction of the works. 

Before passing on to the details of water-works construction it will 
be of assistance to get a general view of the subject, and to that end 
we will here briefly describe the various general features, the arrange- 

19S 





GENERAL ARRANGEMENT OF WATER-V/ORKS. 199 

ment of the various parts of a system, and the standards by which the 
economy of various methods and arrangements can be compared. 

GENERAL ARRANGEMENT OF WATER-WORKS. 

228. Classification.—The various constructive features of a water- 
supply system are divided into three groups: (1) Works for the collec¬ 
tion of water; (2) Works for the purification of water; (3) Works for 
the conveyance and distribution of water. 

229. Works for the Collection of Water.—These are divided according 
to the nature of the source into: (A) Works for taking water from large 
streams and natural lakes; (B) Works for the collection of ground- 
water; (C) Works for the collection of water from small streams by 
means of impounding reservoirs. 

A. Works for taking water from large streams or lakes vary in 
character from a simple cast-iron pipe extending a short distance from 
shore, to the expensive tunnels and cribs of some of the large cities on 
the Great Lakes. The location of these works is determined very 
largely with respect to the quality of the water obtainable. Wherever, 
as is often the case, it is desired to draw a supply from a lake which 
at the same time receives sewage from the city, the question is one 
involving great difficulties. 

B. Works for the collection of ground-water consist of various 
forms of shallow wells, artesian wells, filter-galleries, etc. The 
location of works of this class is determined, primarily, by the location 
of the water-bearing strata. If these are extensive, it will usually be 
convenient and economical to place the wells at relatively low eleva¬ 
tions in order that the water may be readily reached by pumps, or 
perhaps in order that a flowing well may be secured. In the case of 
shallow wells the location is often affected by the possibility of local 
contamination, an element usually absent in the case of deep wells. 

C. Water collected in impounding reservoirs from streams of com¬ 
paratively small watersheds depends for its good quality chiefly upon 
the scarcity of population upon the watershed. Suitable areas are 
therefore more likely to be found in the more rugged parts of the 
country and at the higher elevations, and usually at considerable dis¬ 
tances, sometimes as great as 50 or 75 miles, from the population to 
be served. The location of such impounding reservoirs is also largely 
dependent upon questions of construction, such as the location of the 
dam, length and cost of aqueduct or conduit, and, what is of great 
economic importance, whether the water can be conveyed and dis¬ 
tributed entirely or partly by gravity. 


200 


WA TER- WORKS CONSTRUCTION IN GENERAL. 


230. Works for the Purification of Water.—These vary in kind 
according to the nature of the impurities to be removed. Thus in the 
case of surface-waters the sediment, bacteria, etc., are removed more 
or less completely by settling-basins and various forms of filters; dis¬ 
agreeable gases by aeration. In the case of ground-waters iron may 
be removed by aeration and filtration; hardness by chemical precipita¬ 
tion, etc. In these ways waters otherwise very undesirable can be 
greatly improved or made entirely satisfactory, but of course at a con¬ 
siderable expenditure of money. It will often happen, therefore, that 
a source of good quality but expensive will need to be compared with 
another poor in quality but capable of being made fairly comparable 
with the other at no greater total cost. Not infrequently the possibility 
of the future deterioration of a surface supply and the consequent 
necessity for artificial purification must also be considered. 

231. Works for the Distribution of Water.—These include aqueducts 
and conduits for conveying water from a distant source, pumps and 
pumping-stations, local reservoirs for equalizing the flow or for storage, 
and the pipes for distributing to the consumers. Conduits may be open 
channels, masonry conduits not under pressure, or closed pressure 
conduits, such as pipes of wood, iron, or steel, and sometimes tunnels. 
The form is determined chiefly by considerations of cost. Pumps 
are used in a great variety of forms and situations, and may be operated 
by steam, gas, electricity, wind, or by hydraulic power. There are 
deep-well pumps for drawing water from depths not reached by suction, 
low-lift pumps for raising water from a river into settling-basins or on 
to filters, or from wells into a low reservoir; and high-lift pumps for 
forcing the main supply into the distributing pipes or into an elevated 
distributing reservoir. Local reservoirs are used for receiving water 
from long conduits and regulating the flow in the distributing system, 
for equalizing the flow and pressure in pumping systems, and as settling- 
reservoirs. The pipe system includes distributing mains, fire-hydrants, 
service-pipes, shut-off valves, regulating-valves, etc. 

232. Arrangement of Works,—The arrangement, extent, and cost 
of the various features of a water-works system depend greatly upon 
the nature of the source, its distance from the district to be served, and 
its elevation above that district. 

In describing the various arrangements of water-works systems it 
will be convenient to consider them in two classes: first, those draw¬ 
ing from a distant source; and second, those drawing from a near-by 
source. 

Where the water is obtained from a distant source we may have: 


SYSTEMS OF OPERATION. 


201 


(a) gravity systems in which water from an impounding reservoir or 
lake (rarely from other sources) is led into a conduit through which it 
flows down to the city; or (/>) systems in which the water is pumped 
from ground-water sources, or from rivers or lakes, by low-lift pumps 
into a gravity conduit, or by high-lift pumps directly into a pressure 
Conduit to the city. At the city it passes into a small reservoir and thence 
by gravity to the consumer, or it may be pumped from the reservoir 
to a higher level in order to get the necessary pressure for distribution. 
Where the differences of elevation in the city are great it may be 
economical to have two or more zones of distribution. If the water is 
to be purified, the necessary works may be located at any convenient 
point between the source and the city. If placed at the source, a set 
of low-lift pumps will probably need to be established; if at any other 
point along the conduit, such pumps will seldom be required. 

A near-by source is usually at so slight an elevation above the city 
that high-lift pumps are required to furnish the necessary pressure for 
distribution. With a ground-water source a set of low-lift pumps may 
often be used to elevate the water into a low equalizing reservoir, 
whence it is drawn by the high-lift pumps. If the source is a lake or 
large stream and filters are used, low-lift pumps will usually be required 
to pump the water upon the filters, although gravity may sometimes be 
used for this. If the source is an impounding reservoir, it is occasionally 
at so high a level that a gravity system may be employed. 

The most expensive arrangement is in general a distant source at 
a low elevation where purification is required, such as an impure water 
brought from a distance. The cheapest is a near-by source of pure 
water at a high elevation, such as a spring-water or artesian water 
under pressure. In the nature of things, comparisons between such 
sources will seldom need to be made. Systems requiring careful com¬ 
parison are usually various near-by sources requiring pumping and 
possibly purification with various remote sources of pure water usually 
located at a high elevation. 

233. Systems of Operation.—According to the arrangement of the 
works there are several so-called “systems” of distribution: (1) by 
gravity; (2) by pumping to reservoir; (3) by pumping to stand-pipe or 
tank; and (4) by pumping direct. In (1) the water is conveyed 
entirely by gravity. In (2) it is elevated to a distributing-reservoir, 
whence it flows by gravity into the pipe system. In (3) a small stand¬ 
pipe or tank is substituted for the reservoir, while in (4) the water is. 
pumped directly into the mains. In all these methods the pipe system 
remains essentially the same. 



202 


WATER-WORKS CONSTRUCTION IN GENERAL. 


In many cases a reservoir or standpipe is so arranged that it 
receives only the surplus water when the rate of pumping exceeds the 
demand, and returns this surplus at times when the demand exceeds 
the rate of pumping. This may be considered a combination-of (2) 
and (4) or (3) and (4), and is sometimes called the direct-indirect 
system. Again, it is often desirable in the case of a reservoir or stand¬ 
pipe system to so arrange the piping that in case of fire the reservoir 
may be shut off and an increased pressure furnished directly by the 
pumps. 

The number of works in the United States operated under the 
various systems are given in Table No. 34, compiled by Flynn.* 


TABLE NO. 34 . 


NUMBER OF CITIES AND TOWNS IN THE UNITED STATES SUPPLIED WITH WATER 

BY THE VARIOUS SYSTEMS NAMED. 


System. 


Gravity. 

Gravity and pumping : 

Direct... 

To reservoir. 

To stand-pipe. 

Direct and to reservoir. 

Direct and to stand-pipe. 

To reservoir and stand-pipe. 

Total. 

Pumping : 

Direct. . 

To reservoir. 

To stand-pipe. 

To reservoir and stand-pipe. 

Direct and to reservoir. 

Direct and to stand-pipe. 

Direct and to reservoir and stand-pipe 

Total. 

Natural Pressure. 

Grand total. 


Northeastern 

States. 

Southeastern 

States. 

North Central 
States. 

Western 

States. 

Total. 

490 

41 

II 

194 

736 

62 

7 

2 

15 

86 

38 

1 

2 

13 

54 

II 

2 

2 

5 

20 

I 

0 

O 

1 

2 

3 

1 

3 

1 

8 

4 

0 

0 

8 

12 

119 

11 

9 

43 

182 

74 

33 

221 

90 

418 

128 

62 

79 

114 

383 

245 

139 

218 

358 

960 

26 

11 

14 

20 

7 i 

33 

11 

27 

45 

116 

4 1 

20 

115 

185 

361 

3 

2 

18 

10 

33 

550 

27S 

692 

822 

2342 

0 

9 

2 

10 

21 

1159 

339 

7 i 4 

1069 

3281 


234, Comparison of the Various Systems. — In comparing these 
various systems, their relative advantages and disadvantages should be 
considered in three respects: safety or reliability of operation, economy, 
and convenience. The first element is the most important, particularly 


* Eng. News, 1898, XL. p. 10. 

























































SYSTEMS OF OPERATION. 


203 


for large cities; for in such a case the entire community depends so 
absolutely upon the maintenance of the public water-supply that a 
failure for even a day would be a calamity. In smaller cities and 
towns it would be of much less importance, but yet a very vital factor 
in determining the value of a water-supply to the community. This 
element of safety cannot readily be measured in dollars and cents, but 
the experience of many places having an imperfect plant, and the losses 
resulting therefrom, show that it is a matter justifying a large measure 
of consideration. 

In the matter of economy, differences are more readily measured. 
In comparing the convenience of two systems we should consider the 
amount and uniformity of pressure in the two cases, convenience in the 
operation of pumps and in the making of repairs and renewals, use of 
hose versus fire-engines, etc. All of these involve more or less also 
the question of economy. 

235, Safety. —In respect to safety or reliability of operation the 
gravity system undoubtedly ranks first. The nature of the structures is 
such as to render them little liable to accident, and if a reservoir of 
from 5 to 10 days’ capacity is provided to receive and distribute the 
water from the conduit, thus allowing time for repairs, or if the conduit 
is in duplicate or of masonry underground, this system is exceedingly 
safe and reliable. 

Next to the gravity system in point of safety is the system of 
pumping to an elevated distributing-reservoir holding several days’ 
supply. If at the same time considerable reserve pumping capacity is 
furnished to enable ordinary repairs to be made without drawing largely 
from the reservoir, this system is not far inferior to the gravity system. 
Certain rare though possible contingencies, such as a shortage of fuel 
or a boiler explosion, must, however, be considered as tending to place 
this system second in point of safety. Hydraulic power is in this 
respect more reliable than steam-power. 

Many water-works have' in place of a reservoir a small tank or 
stand-pipe holding at most but a few hours’ supply, dependence being 
placed entirely upon the pumps for any continued excessive draught. 
This arrangement is manifestly inferior to the second system, and should 
not be used if a suitable site can be found for an elevated reservoir. In 
many places where the stand-pipe or the direct-pressure system has 
been in use, elevated reservoirs have subsequently been constructed. 

The system of direct pumping depends for its efficiency entirely upon 
the ability of the pumps to follow all variations in consumption and to 
respond at any instant to demands for fire purposes. It ranks last in 


204 WA TER- WORKS CONSTRUCTION IN GENERAL. 

reliability, and should not be considered except for localities of level 
topography, where it becomes a question between this and the stand-pipe 
system. For small or moderate-sized cities an elevated tank holding 
at least one hour’s fire consumption is an important element of safety 
and greatly to be desired. For large cities the fire rate does not call 
for such a large relative increase in pumping capacity and it can there¬ 
fore be more readily met by the pumps. The total quantity used is, 
moreover, large, and small tanks would be of little value. The pump¬ 
ing machinery in large works is also more likely to be at all times in 
good working condition than is the case with small plants. 

Where a stand-pipe is used for ordinary domestic pressure and 
dependence is chiefly placed on direct pumping for fire purposes, the 
stand-pipe may still be of considerable value in furnishing a fire pressure 
suitable for certain of the lower districts of the town or for small fires 
in the residence portion. 

236. Economy and Convenience. —The relative economy of different 
systems for a given city is a matter depending entirely upon the local 
conditions. Compared to a pumping system, the gravity system is 
very economical of operation, and the depreciation of the plant is also 
likely to be small. If the source is quite remote, the expense of con¬ 
duit becomes an important item, and beyond a certain distance the 
high initial cost will outweigh the economy of operation. As a gravity 
system is usually fed from an impounding-reservoir, there is also 
involved in this case the expense of reservoir construction. 

Comparing the various forms of pumping systems, a large distribut¬ 
ing-reservoir, while adding to the first cost, is an element of economy 
in enabling the pumps to be more uniformly and economically operated 
and in reducing slightly the necessary size of the piping. In small 
works the pumps can thus be operated a convenient number of hours 
each day, such as 8, 10, or 12. A large reservoir will also require a 
less amount of idle pumping capacity for reserve than either the direct 
or the stand-pipe system. With respect to the convenient operation of 
pumps the stand-pipe or tank system is better than the direct; and in 
very small works it may effect a considerable saving by enabling them 
to be operated for but a part of the time. 

As regards uniformity of pressure the gravity and reservoir systems 
are equally good. Direct pumping is the least desirable, but cannot be 
said to be entirely disadvantageous, as the pressure can be more readily 
modified to suit the requirements. Thus the high pressure necessary 
for fire extinguishment may be furnished only so long as it is needed, 
while at other times a much less pressure may be used, a matter of 


THE DUAL SYSTEM. 


20 $ 


considerable economical importance. A similar advantage exists in 
the combined stand-pipe and direct-pressure system, with the addi¬ 
tional one of a more flexible operation of the pumps at ordinary 
times. 

237. Existing Works as Affecting Choice. —The problems of the 
future are mostly those of enlarging and improving present supplies. 
The kind and condition of the system already in existence will there¬ 
fore often be of controlling influence in arriving at the best design for 
the new works. It will often happen that the present source has 
become polluted, and the question arises whether it be best to abandon 
it, to purify the water, or to use the water for other than domestic pur¬ 
poses. Combinations may thus be made between old and new systems 
or sources, and these may be either operated together or independ¬ 
ently, each one serving a separate district, a separate zone of elevation, 
or a separate service. 

238. The Dual System. —It has been proposed that where it becomes 
very expensive to furnish a water suitable for drinking purposes, a 
double system be adopted. One system would furnish water of the 
purest quality for drinking and culinary purposes, while the other would 
supply water for other domestic purposes, and for commercial and 
public use. The former would be perhaps relatively expensive, but as 
the quantity required would be only 5 or 6 gallons per head per day, 
the total expense would not be great. It would also often be much 
easier to find a good water in the quantities required for this purpose 
than for the entire supply. For example, a city of one million inhabit¬ 
ants would require only 5 or 6 million gallons per day of pure water, 
a quantity that could very often be obtained from good ground-water 
sources, such as would be entirely inadequate to supply all the water 
required. The larger quantity could then be obtained from cheaper 
sources, making the total expense in many cases less than under the 
usual single system. 

The chief objection to this double system is the fact that there 
would be in all houses impure as well as pure water, and unless the 
former be very bad, unfit in fact for washing purposes, many persons 
would be careless or indifferent ag to its use and thus the benefits of a 
pure water to a community would be very largely neutralized. That 
such would be the case is indicated by the experience at Lawrence, 
Mass., where, after the introduction of filter-beds to purify the city 
water-supply, a considerable number of cases of typhoid fever still 
remained, most of which were traced to mill operatives who used raw 
canal water at the mills, although city water was readily obtainable. 


2C6 WATER-WORKS CONSTRUCTION IN GENERAL. 

A more practical dual system would be one which would supply the 
purer water for all domestic purposes, and the other and cheaper water 
for certain commercial and public uses. Such a system is in use in a 
number of foreign cities with resulting economy. In Paris, for exam¬ 
ple, where the use of water for street cleaning is so great, a separate 
and cheap supply is used for this purpose. In this country also, a few 
cities have introduced auxiliary supplies, usually for the purpose of 
furnishing increased fire pressure, but in some cases to provide a 
cheaper water for other purposes. The merits of salt water for street 
sprinkling may make it advantageous in towns located on tide-water 
to construct a separate sea-water pipe system. It will also often 
happen that a number of large commercial consumers of water are so 
located that they may be economically supplied with cheap water 
through a separate system. 

PRINCIPLES OF ECONOMIC CONSTRUCTION. 

239. The General Problem.—In fixing upon a design the engineer 
must constantly keep before him the question of economy,—economy 
in the long run and generally speaking. The consideration of this 
question always involves matters relating to the future that can be only 
approximately determined, and On that account it is often very difficult 
to make a correct decision. Thus the cost of operation may, and often 
does, change materially; so also the interest rates, and the cost of 
material, and even the methods of construction. 

The expense of any works to any community is made up of three 
parts: (1) first cost; (2) cost of operation and repairs; and (3) depre¬ 
ciation, or the cost of renewals not included under ordinary repairs. 
The problem of the engineer as regards economy is to secure a mini¬ 
mum sum total of these three items of expense. In addition he must 
usually consider the question of annual payment into a sinking fund. 

240. Methods of Comparing Cost.—Different systems may be com¬ 
pared as to economy either by comparing the value of the capital 
invested and required to keep the plant in operation, or by comparing 
the annual expense, including the depreciation and interest on the 
investment. The former method is frequently employed in comparing 
designs of structures where the first cost is of relatively great importance, 
but for certain purposes it is important to look at the matter from the 
standpoint of annual charges, especially in connection with the financial 
management of the works, provision for payment of bonds, etc. Both 
methods should give the same relative result. 


METHODS OF COMPARING COST. 


20 7 


241. Method of Capitalization.—To correctly state the cost of a 
works in terms of capital we have: (1) the first cost; (2) the annual 
cost of operation and maintenance capitalized at the current rate of 
interest; (3) the capital which must be added to make good the 
depreciation. The last sum must be such an amount as will, when put 
at compound interest, provide a sum at the expiration of the life of the 
structure sufficient to renew it and also to leave a sum equal to the 
original amount for further future provision. These three sums will 
then equal an amount sufficient to construct, operate, and perpetually 
maintain the plant. 

Many parts of a water-works system can be kept in perfect service 
indefinitely by the ordinary repairs. These are not subject to depre¬ 
ciation. Other parts must be renewed from time to time. What are 
considered as repairs, what as renewals, and what as new improve¬ 
ments will depend upon the method of keeping accounts in the particu¬ 
lar water-works considered, but this detail will be left for subsequent 
discussion (Chapter XXIX). 

That part of the cost represented by items (1) and (2) is readily 
stated and requires no further comments. The capital necessary 
to provide for depreciation maybe determined as follows: Let P — 
sum required; C — cost of renewal, assumed equal to the first cost; 
r — rate of interest; and n — years of life of the structure. Then 
placing P at compound interest we must have 


whence 


P(i + r)» = C + P, 

P _ <L _ 

- (i + r y - ! 



If 0 = annual cost of operation and maintenance, we then have the 
total capitalized sum 

5 = c + - + p 

r 

~~ C "T - 4 “ 7 ; St 1 • .... (2) 

1 r (1 + ry — 1 v J 

In permanent structures the term P drops out and the problem reduces 
to a comparison of the first cost plus the capitalized cost of operation, 

C , a very simple matter. With structures not permanent the 

term P must be considered, and this requires a knowledge of the 





208 


WATER-WORKS CONSTRUCTION IN GENERAL. 


durability of the various kinds of structures, and some judgment as to 
their continued usefulness independent of their durability. 

As an example of the method of computation of the total capital 
required suppose that a certain structure costs $50,000; that the 
operating expenses are $5000 per year, and that the life of the struc¬ 
ture is thirty years. If money is worth 5 per cent, the total capitalized 
cost will be, substituting in eq. (2), 


5000 50,000 

S = 50,000 + —77- + 


= $50,000 4- $100,000 $15,000 


.05 ‘ (1.05) 30 — 1 

= $165,000. 

If this same structure would last forty years, the last term becomes 

-— ^ Q ^ QQ - = $8300, and the total capital $158,300; if fifty years, 

the last term becomes $5200, and the total capital $155,200. It is to 
be noted from these figures that to make the structure last forty instead 
of thirty years would justify an initial expenditure of $15,000 — $8300 
1= $6700; to make it last fifty years, an additional expenditure of but 
$3100, and to make it last indefinitely, only $5200 more. Compared 
to first cost and cost of operation, it is thus evident that the question 
of extending the life of a plant by adding to the first cost, when that 
life is already twenty-five or thirty years, is a very minor consideration. 
This example shows also that no great accuracy is necessary in esti¬ 
mating the life of a plant when it is of a fairly permanent character. 

Many other elements enter in to modify these mathematical results. 
For example, inconvenience of renewal, and reliability of operation, 
tend greatly to increase the value of a permanent structure; while 
future improvements in methods and processes tend in the opposite 
direction. 

242. Method of Annual Expense.—The annual expense will be equal 
to the interest on the first cost, plus the cost of operation, plus the 
annual depreciation. It is evidently equal to the interest on the total 
capitalized cost as previously found, or to Cr 4- OPr. The last 
term of this expression is thus the annual depreciation, and by substitut¬ 
ing from eq. (1) we have, letting P — annual depreciation, 


D = Pr = 


Cr 


( 3 ) 


(1 4- r T — 1 ’ 

in which C = cost of renewal (= first cost), r = rate of interest, and 
7 t — life of plant in years. The annual rate of depreciation per unit of 
r 

cost = 


(, + r T - 1 ' 







PROVISION FOR A SINKING FUND. 


209 


The annual depreciation may be otherwise expressed as the annual 
payment which if placed at compound interest will accumulate a fund 
equal to C at the end of n years. Formula (3) assumes the pay¬ 
ment to be made at the end of each year. Table No. 35 gives the 
value of n corresponding to various annual payments and various rates 
of interest, or, what is the same thing, the life of a plant corresponding 
to various rates of annual depreciation. It can be used either with n 
or D as the argument. Thus if the life of a structure is estimated at 
thirty years and the interest rates are 3 per cent, the annual deprecia¬ 
tion will be about 2 per cent of the first cost. 

TABLE NO. 35. 

NUMBER OF YEARS REQUIRED TO ACCUMULATE ANY GIVEN SUM WHEN VARIOUS PER¬ 
CENTAGES OF THE SUM ARE PAID IN EACH YEAR AND PLACED AT VARIOUS 
RATES OF INTEREST. 


Amount Paid Each 
Year or Annual 
Depreciation, D. 

Rates of Interest. 

3%. 

3%. 

4 %• 

5* 

Per cent of first cost 

Years. 

Years. 

Years. 

Years. 

i . 

8l 

66 

56 

49 

I . . 

56 

47 

41 

37 

ii . 

43 

37 

33 

30 

2. 

35 

3 i 

28 

26 

2i . 

30 

27 

24 

23 

3 . 

26 

24 

22 

20 

4 . 

21 

19 

18 

17 

5 . 

17 

16 

15 

14 

6. 

14 

14 

13 

12 

8. 

11 

11 

11 

10 

10. 

9 

9 

9 

8 





- 


Provision for a Sinking Fnnd .—Where bonds are issued to cover 
the first cost of a works it is usually considered good policy to provide 
a sinking fund for the entire liquidation of the debt at the end of some 
long period, such as thirty or forty years. While this question does 
not strictly enter into a determination of the true economy of a struc¬ 
ture, yet the matter of required annual payment for several years to 
come is usually of the most vital importance to the present generation. 
To what extent a sinking fund should be considered in comparative 
estimates is not easy to say. It depends on what the policy of the 
water department is likely to be. Probably very few departments pro¬ 
vide funds to fully cover depreciation, and also a sinking fund. The 
latter is indeed likely to be the chief consideration, and the matter of 
renewals left to the future. In some cases, especially those relating 

























210 


WATER-WORKS CONSTRUCTION IN GENERAL. 


to the improvement of supplies of large cities, it will be well to make 
full allowance for both depreciation and sinking fund, but in most cases 
it w-ould appear to be a fairer basis of comparison and a sufficient pre¬ 
caution against unforeseen contingencies, to omit the sinking fund and 
to consider the permanent parts of the plant as subject to a slight 
depreciation, such as would correspond to a life of forty or fifty years. 

If account is to be taken of annual payments into a sinking fund, 
the amount necessary to accumulate any given sum can easily be deter¬ 
mined from Table No. 35. 

243. Depreciation of Structures.—The rate of depreciation, or the 
life of various parts of a water-works, is very various. With certain 
parts, such as dams, masonry aqueducts, and the like, the life with 
ordinary repairs is practically indefinite. Brick and stone buildings are 
subject to a small depreciation. Pipes buried in the ground have a life 
not yet well determined and which depends much on the character of 
the soil. Cast iron, properly coated, appears to depreciate very 
slightly, if at all. Its life is variously estimated at from thirty to 
seventy-five years, or more. Probably fifty years would usually be 
a safe figure. Carefully protected riveted pipe will also have a very 
long life, but probably not so long as cast iron. Large, well-made 
machinery may have a life of thirty or forty years, or perhaps longer, 
but improvements in the design of machinery would usually limit its 
useful life to twenty-five or thirty years. The life of boilers is com¬ 
monly taken at about twenty years. Light machinery will have a life 
of fifteen or twenty years, and in some cases of great wear even less 
than this. 

244. Provision for the Future.—In the preceding discussion the 
matter of permanence only has been mentioned. Another very im¬ 
portant element needs to be considered at all points of the design, 
namely, what provision is it economical and expedient to make for the 
future ? The questions of future population and consumption have 
already been discussed, and it is here assumed that these have been 
settled. There remains then to be determined the capacity of the 
various parts of the work. Obviously those portions of the works that 
can be as easily added to at one time as another, such as pumps, 
filters, etc., should be built for but little more than present require¬ 
ments. Future requirements, however, should be regarded rather 
more than strict economy would suggest owing to delays and difficulties 
in securing appropriations, etc. Other parts, such as pump-houses, 
land for filter-beds, pumping-mains, etc., should be designed for a 
longer time in the future, as these are obtained more cheaply per unit 


ESTIMATES OF COST. 


21 I 


of capacity at first than by duplication. Still other parts, such as 
masonry conduits, dams, tunnels, etc., should be built for a still 
greater capacity, as the extra cost and depreciation will both be 
relatively small. 

The question to be answered is, how much will it pay to spend now 
in securing capacity in the various parts of the works in order to avoid 
the expenditure of a larger sum in the future ? It is a simple problem 
in compound interest, and is solved by determining what sum of money 
placed at compound interest will amount to the sum saved at the time 
the increased capacity becomes necessary. If A — amount saved at 
the end of n years by incurring a certain expense B at the present time, 
and r — rate of interest, then in order that the one plan may just 
balance the other we have A = B(i -}- r) n , or 


B = 


A 


(I + r)- 



If the structure under consideration is subject to depreciation, the 
amount A must be figured on the basis of the actual value of the 
depreciated plant at the given time in the future. 

To arrive at a proper solution it is necessary to take into considera¬ 
tion many other elements than merely the mathematical one of interest. 
All parts of a works should be made to correspond, or be so designed 
that future enlargements of one part will correspond to the more 
permanent structures of another part. Thus a metal portion of a con¬ 
duit may well be made just one-half or one-third the capacity of the 
masonry portion of the same, the former providing for ten or fifteen 
years in the future, while the latter provides for thirty or forty years. 
There must also be considered the question of the financial ability of 
the community to incur a large expense or a large annual payment, 
the debt limit, etc. These factors will often necessitate the construc¬ 
tion of a plant which might not be the ideal one with unlimited capital 
at hand. 

245. Estimates of Cost.—To be of much value an estimate of cost 
must be made from classified estimates of the different kinds of work 
to be done and material to be furnished. In work of the nature of most 
of that involved in water-works construction the risk is not great, and 
close estimates can be made of the cost of various classes of work by 
inquiry of local contractors and by comparison with the cost of similar 
work already executed. The contract prices quoted in the technical 
papers will be of assistance in this connection. The analysis of the cost of 






212 


WA TER- WORKS CONSTRUCTION IN GENERAL. 


various classes of masonry given in Baker’s “ Masonry Construction 
will also be found useful. Prices of metal parts, such as pipes, valves, 
machinery, etc., vary so greatly from time to time that any statement 
of them would be of little permanent value. Approximate prices can 
always be obtained on short notice by correspondence with manufac¬ 
turers. 

Although the classified estimate is the only reliable way of estimat¬ 
ing the cost of a works, yet it is very useful to an engineer, when consid¬ 
ering the possibilities of different schemes, to have in mind certain 
rough general figures of cost of the different parts of a system. Such, for 
example, as the cost of small pipe systems per mile, cost of reservoirs 
of different kinds per 1000 or 1,000,000 gallons capacity, cost of filters 
per million gallons capacity, etc. In what follows such general figures 
of the cost of works have in many cases been given, but it must be 
remembered that they can be used only in making rough preliminary 
estimates. 


LITERATURE. 

1. Francis. Some Notes on Different Systems of Water-supply. Eng. 

News , 1886, xv. p. 165. 

2. Ellis. Fire Protection by Direct High Pressure from Pumps in Combined 

Pumping and Reservoir, or Stand-pipe Systems. Jour. New Eng. 
W. W. Assn., 1892, vii. p. 27. 

3. McElroy. City Water-supplies of the Future. Eng. Mag., 1894, vi. 

p. 821. 

4. Brackett. Water-supply of Different Qualities for Different Purposes. 

Report Mass. Board of Health on Metropolitan Water-supply, 1895, 
p. 217. 

5. Axtell. Pure Water for Drinking and Cooking. Eng. Mag., 1896, xi. 

p. 67. 

6. Sources, Modes of Supply and Filtration of Public Water-supplies in the 

United States. Eng. News, 1898, xl. p. 9. 

7. Crowell. Report of a Proposed Sea-water Fire Pipe-line for the City of 

New York, 1897. Eng. Record, 1898, xxxvii. p. 124 . 

8. Weston. The Separate High-pressure Fire-service System of Providence, 

R. I. Jour. New Eng. W. W. Assn., 1898, xm. p. 85. 

9. Miller. Report on a Proposed Salt-water Street-sprinkling Plant at 

Oakland, Cal. Eng. News, 1899, xlii. p. 149. 

Auxiliary Water-supplies. Eng. Record, 1899, xl. P- 314. Chiefly 
abstracted from a paper by W. T. Pierce before the British Assn. 
W. W. Engs. 


CHAPTER XII. 


HYDRAULICS. 

246. Purpose of the Chapter.—In the present chapter it is proposed 
to give in as brief a form as possible such hydraulic formulas as are of 
frequent use in the design of water-works, together with diagrams and 
tables of coefficients based upon the latest and most reliable experi¬ 
ments. 

247. Units of Measure.—The unit of length most frequently used in 
hydraulics is the foot. The unit of volume is the cubic foot or the 
United States gallon. The unit of time usually employed in hydraulic 
formulas is the second, but in many water-supply problems the minute, 
the hour, and the day are also often used. The unit of weight is the 
pound, and that of energy the foot-pound. 

1 U. S. gallon = 231 cubic inches = 0.1337 cubic foot; 

1 cubic foot = 7.481 U. S. gallons; 

1.2 U. S. gallons = 1 imperial gallon. 

248. Notation.—The following general notation will be used in the 
present chapter without further explanation: 

w = weight of a cubic foot of water assumed equal to 62.5 pounds; 

g = acceleration of gravity =32.2 feet per second per second; 

h — head of water; 

p — pressure of water; 

r — hydraulic mean radius; 

^ = sine of slope of hydraulic grade-line or of free water-surface; 

Q — rate of discharge or flow; 

v = velocity. 

249. Weight of Water.—The weight of distilled water at different 
temperatures is given in Table No. 36. 

The weight of ordinary water is greater than that of distilled water 
on account of the impurities contained. For ordinary purposes a 
cubic foot of fresh water may be taken equal to 62.5 pounds. Sea¬ 
water will weigh about 64 pounds per cubic foot. 


213 






214 


HYDE A U LICS. 


TABLE NO. 36. 

WEIGHT OF DISTILLED WATER. 


Temperature, 

Fahrenheit. 

Weight,Pounds 
per Cubic Foot. 

Temperature, 

Fahrenheit. 

Weight.Pounds 
per Cubic Foot. 

32 ° 

62.42 

I4O 0 

61.39 

39-3 

62.424 

160 

61.OI 

60 

62.37 

180 

60.59 

80 

62.22 

200 

60.14 

IOO 

62.00 

212 

59*84 

120 

61.72 




250, Pressure of the Atmosphere.—In problems pertaining to the 
operation of suction-pipes it is important to know the atmospheric 
pressure corresponding to various elevations above sea-level. Data 
pertaining to this point are given in Table No. 37 in terms both ot 
mercury barometer and of water barometer. The figures given are 
average values. 

TABLE NO. 37. 

ATMOSPHERIC PRESSURE AT DIFFERENT ELEVATIONS. 


Elevation 
above Sea-level 
Feet. 

Pressure in 
Pounds per 
Square Inch. 

O 

14.7 

500 

14*5 

1,000 

I4.2 

2,000 

13*7 

4,000 

12.7 

6,000 

11.8 

8,000 

11.0 

10,000 

10.3 


Height of 
Mercury 
Barometer. 
Inches. 

Height of 
Water 
Barometer. 
Feet. 

30.00 

34-0 

29.47 

33*3 

28.94 

32.8 

27.92 

31.6 

25.98 

29.4 

24.18 

27.4 

22.50 

25*5 

20.93 

23*7 


251. Vapor Tension of Water.—Where the temperature of the water 
is high the elevation of the water barometer will be considerably 
reduced below that given in the previous table on account of the 
pressure of the water vapor. Table No. 38 gives values of this vapor 
tension or pressure in feet of head for various temperatures. 

252. Pressure of Water.—(1) Pressure at a Point. — The pressure 
of water per unit of area at a distance h below the free surface is 


p — wh 


(0 


























PRESSURE OF WATER. 


215 


TABLE NO. 38 . 

VAPOR TENSION OF WATER. 


Temperature, 

Fahrenheit. 

Pressure in 
Pounds per 
Square Inch. 

Pressure in 
Feet of Water. 

32° 

.09 

.21 

40 

.12 

.28 

6o 

.26 

.60 • 

8o 

•50 

I -15 

IOO 

•95 

2.I9 

120 

I.69 

3-91 

140 

2.89 

6.68 

160 

4-74 

11.0 

180 

7-53 

17.4 

200 

11-56 

26. 7 

212 

14.70 

34 -o 


If h is expressed in feet, and p in pounds per square inch, we have 


p = 0.434^.(2) 

and h — 2.304/.(3) 


Pressures are very commonly stated in terms of the head h , in which 
case h is called the pressure-head. 

(2) Pressure on a Surface .—The pressure of water on a plane sur¬ 
face is always normal to that surface. The amount of the pressure is 

P = wAh, .( 4 ) 

where A = total area of surface, and h — head of water at its centre 
• of gravity. The component of the pressure in any given direction is 
equal to the normal pressure upon that projection of the given surface 
at right angles to the given direction. 

(3) Centre of Pressure .—The centre of pressure upon a submerged 
plane surface is given by the formula 

y = .( 5 ) 

where y — distance of centre of pressure from the intersection of the 
plane with the water-surface; and 1 and 5 are respectively the moment 
of inertia and the statical moment of the area about this intersection. 












2 l6 


HYDRA U LICS. 


(4) Bursting-pressure in Pipes .—The bursting-pressure per lineal 
unit in a pipe of diameter d, due to a water-pressure /, is 

P, = pd. .( 6 ) 

If t = thickenss of pipe, the resulting tensile stress per unit area is 


_ fj - P 

2 1 2 t 


• • ( 7 ) 


In a closed cylinder under pressure the force tending to rupture it 
transversely is 

pnd 2 


p, = 


and the stress per unit area is 


P a 


a% ~ ndt 


pd 

4 *’ 


( 8 > 


( 9 ) 


or one-half that given by equation (7). This is also the stress in a. 
sphere of diameter d. 

Formulas (6) to (9) assume that the water in the pipe or cylinder 
is under a uniform pressure, or, in other words, that the diameter of 
the pipe is small as compared with the pressure head of the water. 

FLOW OF WATER THROUGH ORIFICES. 

253. Form and Proportion of Orifices.—In making use of an orifice 
for measuring water it is desirable that it be made in such a way as to 
be in effect an orifice in a thin plate; that is to say, it should be sa 
arranged that the water in passing out will touch the inner edge only. 
Furthermore, it is important that the inner edge of the orifice shall be 
flush with the inner surface of the tank, and that the latter should 
extend as a plane surface for a considerable distance in each direction 
from the orifice. To secure complete contraction the orifice should be 
placed at a distance from the sides and the bottom of the tank not less 
than three times the width of the orifice; and in order that the effect 
of the velocity of approach may be inappreciable the area of the orifice 
should not exceed one-twentieth of the cross-section of the tank. 

254. Flow through Small Orifices.-—The theoretical velocity of water 
flowing through an orifice is, at the point of contraction, v — V 2 g/i> 
where h — head of water at centre of orifice. The actual velocity is a 
little less than the theoretical, and we have 


V = C V2gk, 


(10) 










FLO W OF WATER THROUGH ORIFICES. 217 

in which ^ is a coefficient, found by experiment to be equal to .97 to 
.98. The ratio of the area of the cross-section of the contracted vein 
to the area of the orifice is called the coefficient of contraction. It 
ranges from .6 to .7, but usually has a value of from .62 to .64. 
Finally, if A — area of orifice, the discharge is 

Q — c d A V 2 gh, .(n) 

in which c d = coefficient of discharge = about .62. Many experiments 
have been made to determine the value of c d directly. 

255. Large Rectangular Vertical Orifices.—The discharge is given 
by the formula 

Q = c . %b 4/2 g(lil — k*) t .(12) 

in which c is again a coefficient, b = width, h 2 = head on lower edge 
of orifice, and h l — head on upper edge. If the head h at the centre 
of the orifice is greater than four times the height of the orifice, then 


it is sufficiently exact to write 

Q = c . bd V 2 gh, .(13) 

in which d — vertical dimension of the orifice. For square orifices 

* 

b — d } and if h is greater than 4 d, then 

Q = c . d 2 V2gh .(14) 


Table No. 39 contains values of coefficients for square orifices as 
deduced by Hamilton Smith from the results of many experiments. 

TABLE NO. 39 . 


COEFFICIENTS FOR SQUARE VERTICAL ORIFICES (SMITH). 


Head, h , 



Side of the Square in Feet. 



in Feet. 

0.02 

0.04 

0.07 

0.1 

0.2 

0.6 

I .O 

0.4 

0.6 

0.660 

0.643 

.636 

O.628 

.623 

0.621 

.617 

0.605 

0.598 


0.8 

.652 

.631 

.620 

.615 

.605 

.600 

0-597 

I .O 

.648 

.628 

.618 

.613 

.605 

.601 

•599 

I • 5 

.641 

.622 

.614 

.610 

.605 

.602 

.601 

2.0 

.637 

.619 

.612 

.608 

.605 

.604 

.602 

2.5 

.634 

.617 

.610 

.607 

.605 

.604 

.602 

3 

.632 

.616 

. 609 

.607 

.605 

.604 

.603 

4 

.628 

.614 

.608 

.606 

.605 

.603 

.602 

6 

.623 

.612 

.607 

.605 

. 604 

.603 

.602 

8 

.619 

.610 

. 606 

.605 

. 604 

.603 

.602 

10 

.616 

.608 

.605 

.604 

.603 

.602 

.601 

20 

.606 

.604 

.602 

.602 

.602 

.601 

.600 


.602 

.601 

.601 

.600 

.600 

•599 

•599 

100 

•599 

•593 

•598 

.598 

•598 

•598 

•598 






























218 


H YD R A UL1CS. 


256. Circular Vertical Orifices.—The discharge from large circular 
vertical orifices is given by the formula 


1 d 2 


Q=c. \nd 2 V 2 gh\i — —g-r i — 


5 d‘ 


105 


128 h 2 16,384 A 4 4,194,304 


d« 

etc. 


(' 5 ) 


where d — diameter of orifice, and h — head of water at its centre. 
If h is greater than 3 d, then we may write 


Q = c . \nd 2 \ / 2 gh .(16) 

Table No. 40 gives values of c as deduced by Hamilton Smith. 


TABLE NO. 40 . 

COEFFICIENTS FOR CIRCULAR VERTICAL ORIFICES (SMITH). 


Diameter of Orifice in Feet. 


Head, h.. 


in Feet. 

0.02 

O.O4 

O.O7 

0.10 

0.2 

0.6 

1.0 

0.4 

0.6 

0.655 

0.637 

.630 

• 

0.624 

.618 

0.618 

.613 

0.601 

0.593 


0.8 

.648 

.626 

.615 

.610 

.601 

• 594 

0.590 

1.0 

.644 

.623 

.612 

.608 

.600 

• 595 

• 591 

i -5 

•637 

.618 

.608 

. 605 

.600 

• 596 

• 593 

2.0 

.632 

.614 

.607 

.604 

•599 

• 597 

.595 

2-5 

. 629 

.612 

.605 

.603 

•599 

• 598 

• 596 

3 

.627 

.611 

.604 

.603 

•599 

• 598 

• 597 

4 

.623 

.609 

• 603 

.602 

•599 

.597 

• 596 

6 

.618 

.607 

.602 

.600 

•598 

• 597 

• 59 6 

8 

.614 

.605 

.601 

.600 

•598 

.596 

.596 

10 

.611 

.603 

•599 

• 598 

•597 

• 596 

•595 

20 

. 601 

•599 

•597 

• 596 

•596 

• 596 

•594 

50 

• 50 

•595 

•594 

' -594 

•594 

•594 

•593 

100 

•593 

•592 

•592 

• 59 2 

•592 

• 592 

•592 


FLOW OF WATER OVER WEIRS. 

257. Sharp-crested Weirs. — For measuring the flow of a small 
stream a weir is very often employed. Such weirs are usually rectan¬ 
gular and are made sharp-crested, that is, of a form such that the water 
touches the inside edge only. The back of the weir should be a 
vertical plane surface. If the ends of the weir are placed at some dis¬ 
tance from the sides of the channel, the stream of water will be 
contracted laterally. For complete contractions this distance should 
be at least three times the height of the weir. If the ends are flush 
with the sides of the channel, there will be no end contractions. 

































FLOW OF WATER OVER WEIRS. 2 19 

The depth of the water on a weir should be measured sufficiently 
far above the weir to eliminate the effect of the surface curve. 

The formula for discharge from a rectangular weir may be written 
from equation (12) by putting h 1 = o. It is 

Q = c . \l V 2 gH‘\ .(17) 

where l — length of weir and H — height of water on the weir. If the 
channel is small, the velocity of approach will have an appreciable 

effect upon the discharge. If h — head due to this velocity = —, 

2g 

then this factor is commonly taken account of by the use of the equa¬ 
tion 

Q — c . -§/ Si'2g(H + nhf, .... ( 18 ) 

in which n is a coefficient varying from 1 to 1.5. The velocity of 
approach can be estimated with sufficient accuracy by first determining 
the value of Q with the term nh omitted, then using this value of Q to 
determine v , and then a more accurate value of Q , etc. From a care¬ 
ful analysis of the experiments of Francis, Fteley and Stearns, and 
others, Hamilton Smith has adopted values for n of 1.4 for weirs with 
end contractions, and 1^ for weirs with contractions suppressed. From 
his study of the experiments referred to he has also derived the 
values for the coefficient c as given in Tables Nos. 41 and 42. 

TABLE NO. 41 . 


COEFFICIENTS FOR CONTRACTED WEIRS (SMITH). 


Effective 



Length of Weir in Feet. 



Head in 
Feet. 

0.66 

I 

2 

3 

5 

TO 

19 

O. I 

O. 632 

0.639 

0.646 

0.652 

0.653 

0.655 

0.656 

O.15 

. 619 

.625 

.634 

.638 

. 640 

.641 

.642 

0.2 

.6ll 

.618 

. 626 

.630 

.631 

•633 

•634 

0.25 

.605 

.612 

.621 

.624 

.626 

.628 

. 629- 

0-3 

.601 

.608 

.616 

.619 

.621 

.624 

.625 

0.4 

• 595 

.601 

. 609 

.613 

.615 

.618 

.620 

0*5 

•590 

•596 

.605 

.608 

.611 

.615 

.617- 

0.6 

.587 

•593 

. 601 

.605 

.608 

.613 

.615 

0.7 


•590 

• 598 

.603 

.606 

.612 

.614 

0.8 

0.9 

1.0 

1.2 

1.4 

1.6 

* 


• 595 
.592 

• 590 

.585 

.580 

.600 
•598 
• 595 
• 59 i 
.587 
.582 

.604 
.603 
.601 
• 597 
•594 
• 59 i 

.611 

. 609 
.608 
.605 
.602 
.600 

.613 
.612 
.611 
. 610 
. 609 
.607 



































2 20 


HYDRA ULICS. 


TABLE NO. 42 . 

COEFFICIENTS FOR SUPPRESSED WEIRS (SMITH). 


Effective 



Length of Weir in 

Feet. 



Head in 
Feet. 

*9 

10 

7 

5 

4 

3 

2 

O. I 

O. 15 

0.657 

• 643 

0.658 

.644 

O.658 

•645 

O.659 

.645 

O.647 

O . 649 

0.652 

O. 2 

•635 

•637 

.637 

.638 

.641 

.642 

• 645 

0.25 

.630 

.632 

.633 

.634 

.636 

.638 

.641 

o -3 

. 626 

.628 

.629 

.631 

•633 

.636 

.639 

0.4 

.621 

.623 

.625 

.628 

.630 

•633 

.636 

0.5 

.619 

.621 

.624 

.627 

.630 

•633 

•637 

0.6 

.618 

.620 

.623 

.627 

.630 

•634 

.638 

0.7 

.618 

.620 

.624 

.628 

.631 

•635 

.640 

0.8 

.618 

.621 

.625 

.629 

•633 

•637 

.643 

0. g 

.619 

.622 

.627 

.631 

.635 

•639 

645 

1.0 

.619 

. 624 

.628 

•633 

•637 

.641 

.648 

1.2 

.620 

. 626 

.632 

.636 

.641 

.646 


1.4 
i .6 

4 

.622 

.623 

.629 

.631 

•634 

•637 

.640 

.642 

.644 

.647 




Mr. James B. Francis from his elaborate series of experiments 
Lowell* on a weir io feet long - , and operating under heads of 0.4 to 
1.6 feet derived the formula for weirs without end contractions, 


Q - Z - lllH 1 .(19) 

and with contractions 

Q = 3-33(7 - 0.2 H)H l .(20) 

If there be but one contraction, 0.1H is to be used instead of 0.2H. 
To take account of the velocity of approach, the formulas become 

Q = 3-3340^ + ~ ^ 5 ]».(21) 

and Q = 3-33(/ — o. 2 H)[(HJif — k% . . . (22) 

v 2 

in which h— —. In these formulas the unit of length is the foot. 

2g 

The most elaborate series of experiments on weirs ever made is 
that which has been carried out by Bazin, and which is reported in the 
Annals des Ponts et Chaussees for the years 1888-98. The formula 
deduced by him for sharp-crested weirs with no end contractions is in 
foot units 

Q = (.405 + + .5 . • (23) 


* Lowell Hydraulic Experiments. New York, 1S71. 




























FLOW OF WATER OVER WEIRS. 


221 


in which p — height of weir above the bottom of the channel, and h is 
the actually observed head on the weir. The velocity of approach is 
taken account of in the formula. This formula gives slightly larger 
values for the discharge than the Francis formula.* 

258. Submerged Weirs.—As the result of an analysis of the experi¬ 
ments of Francis and of Fteley and Stearns, Mr. Herschel t adopts the 
following formula for discharge, for submerged, sharp-crested weirs 
without end contractions: 

Q=3-33l(*H)'; .(24) 

where / = length of weir; 

H — height on the weir on the up-stream side; 
n = a coefficient, depending on the ratio of the head on the 
down-stream side H' to the head H. 

The values of n are gi^en in Table No. 43. 

TABLE NO. 43 . 


VALUES OF tl FOR SUBMERGED WEIRS. (HERSCHEL.) 


H' 

H 

n 

H> 

H 

n 

H' 

H 

n 

H ' 

H 

n 

• OO 

I .OOO 

. 20 

O.985 

•45 

O.912 

•70 

O.787 

.02 

1.006 

.25 

0-973 

• 50 

O.892 

•75 

0.750 

•05 

1.007 

.30 

0.959 

•55 

O. 871 

.80 

0.703 

. IO 

I .005 

•35 

0-944 

.60 

O. 846 

.90 

0-574 

•15 

O. 996 

.40 

O.929 

.65 

O.819 

I. OO 

0.000 


259. Weirs of Varying Section.—In many cases it is desirable to 
determine the flow of a stream by measurements taken of the height of 
water flowing over some dam or weir; and, on the other hand, in the 
design of waste-weirs some method of estimating their capacity is 
essential. The law of flow over such weirs is very complicated, and 
the only accurate way of determining the constants for any particular 
case is by means of experiments on a section of the same form as the 
one in question. If this is impossible, the best substitute for it is to use 
constants which have been determined for a weir agreeing as closely 
in form as may be to the one under consideration. 

Here again Bazin’s work is of the greatest value. He employed 
in his experiments weirs of a great variety of form. The heights used 
were one metre and one and one-half metres; and the heads employed 
reached a maximum of about one-half metre. The end contractions 

* See a valuable paper by G. W. Rafter, including exhaustive discussion, in 
Trans. Am. Soc. C. E., Dec. igoo. 

f Trans. Am. Soc. C. E., 1885, xiv. p. 194. 


























222 


HYDRAULICS. 


were suppressed in all cases, and below the weir the sides of the 
channel were continued so that in general there was not perfectly free 
access of air beneath the sheet of water. In Table No. 44 are given 
values of the coefficient C in the formula Q = ClJu, for several forms 
of weirs, as deduced from Bazin’s experiments. The head h is in all 


TABLE NO. 44 . 

VALUES OF THE COEFFICIENT C IN THE FORMULA Q=ClM, FROM BAZIN’S EXPERIMENTS. 
























































FLOW OF WATER OVER WE IRS. 


223 


TABLE NO. 44 .— Continued. 


Height of Weir in Feet. 


No. 


Section of Weir. 




0.4 

0.6 

0.8 

1.0 

1.2 

1.4 

3-44 

3-64 

3.80 

3-94 

4.04 


3.18 

3-34 

3-49 

3-65 

3-79 

3-90 

2.77 

2.83 

2.92 

3-05 

3 -i 6 

3.29 

3-08 

3-33 

3-49 

i 

3*54 

3- 60 

3-64 

3-24 

3-40 

3.60 

3-76 

3-86 

3-97 

3-04 

3.12 

3-19 

3.26 

3.36 

3*48 

3.06 

3.10 

3-14 

3.18 

3-20 

3.23 

2.83 

3-oo 

3-15 

3-27 

3-38 

3-47 

3-56 

3-54 

3.57 

3-62 

3-66 

3 - 7 <? 

3-12 

3.23 

3-34 

3-47 

3-56 

3-^4 

2.80 

2.85 

2.90 

2.97 

3-05 

3- 1 4 

2.86 

2.88 

2.93 

2.96 

2.98 

3-oo 

3-40 

3-76 

4.08 

4-36 

4.56 

4-56 

























































224 


HYDRA ULICS. 


TABLE NO. 45 . 

VALUES OF THE COEFFICIENT C IN THE FORMULA Q = Clh*, FROM THE CORNELL 

UNIVERSITY EXPERIMENTS. 


<u 

& 

6 

p 

2 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 


Height on Weir in Feet. 


Section of Weir. 





x-5 

a.o 

2.5 

3-o 

3-5 

4.0 

4-5 

5.0 

3-51 

3-37 

3-33 

3-3i 

3-29 

3-23 

3- l6 

3-14 

3-51 

3-37 

3-33 

3-3i 

3-29 

1 

3-25 

3-20 

3-21 


3-76 

3-68 

3-68 

3-70 

3-75 

3-83 



3-68 

3.71 

3.81 

3-90 

4.00 

4.06 


3-8i 

3.61 

3.68 

3-65 

3-72 

3.80 

3-93 



2.85 

2.89 

3.03 

3*16 

3*30 

3-50 

3-71 


3.12 

3.20 

3-31 

3-45 

3.63 

3-78 

3-9* 



2-45 

2.49 

2.51 

2.56 

2.59 

2.67 

2-93 

2.85 

2.82 

2.90 

2.90 

2.92 

2-95 

#' 

3*29 

3-23 

3-34 

3-42 

3-45 

3*47 

3.52 

' T 

3-51 

3-52 

3-47 

3*55 

3.62 

3-68 

3-72 


3-59 

3-62 

3-54 

3.52 

3-57 

3-55 

3-69 


3.81 

3.61 

3-57 

1 

3-u 3 

3-62 

3*67 

3-7* 

3 * 80 

3-37 

3.20 

3-50 

J 
2.60 , 

1 

V’o j 

5.84 ] 

3-Qb j 
























































































FLOW OF WA TER THROUGH PIPES. 


225 


cases the actually observed head on the weir. The coefficients as 
given were obtained from curves plotted from Bazin’s results.* 

More recently Mr. G. W. Rafter and Prof. G. S. Williams have 
made for the United States Board of Engineers on Deep Waterways 
an important series of experiments at the Cornell University Hydraulic 
Laboratory, t In these experiments the height of water on the weir 
was carried to a value of about 5 feet, the weir being 6.58 feet long 
and from 4.6 to 4.9 feet above the bottom of the channel. Free 
access for the air beneath the sheet of water was provided. In Table 
No. 45 are given coefficients for several of the forms experimented on, 
for use in the formula Q = Cllfy where h is again the actually observed 
head on the weir. These values were deduced from the data and dis¬ 
charge curves given in Prof. Williams’ discussion of Mr. Rafter’s paper 
above referred to. 

It is important to note that, on account of the difference in condi¬ 
tions with respect to the entrance of air below the sheet of water in the 
two series of experiments above described, it appears that in those 
forms having a steep down-stream face the coefficients from Bazin’s 
-experiments are much the higher. For slopes greater than one-to-one 
the differences are small. Note also that weirs with wide crests give 
lower coefficients than those with narrow crests; also that low weirs 
give higher coefficients than high weirs. 

FLOW OF WATER THROUGH PIPES. 

260. General Relations between Velocity and Pressure.—Let A BCD, 
Fig. 32, be any pipe in which there occurs a steady flow of water from 



a reservoir. Let h v h 2 , etc., be the pressures in this pipe at points 
B y C y D, etc.; let z v z 2 , z s , etc., be the elevations of the pipe at these 
points above any given plane, and H Q the elevation of the surface of 
the water in the reservoir above this plane. Letz^, v 2 , v v etc., be the 

* See Rafter’s paper in Transactions Am. Soc. C. E., Dec. 1900, for a compilation 
of Bazin’s coefficients. 

f Trans. Am. Soc. C. E., Dec. 1900, pp. 266, 316. 




















226 


HYDRA ULICS. 


velocities at the several points; they will be inversely proportional to 

the respective cross-sections of the pipe. The total energy, potential 

and kinetic, of any given volume of water, referred to the datum plane 

£,2 

and expressed in terms of head or elevation is, li -[- z -j- —, or 


H + 



then 


If there be no loss of energy in passing from point to point, 


h z — = a constant, 

^ ^ 2 g 



which is Bernoulli’s theorem. 

In the flow of water through pipes some loss of energy takes place, y 
or rather is dissipated as heat because of the internal friction in the 
water, so that the value of the expression written above, instead of 
remaining constant, becomes continually smaller as the water advances. 

If hf — loss of head due to friction between points B and C , we may 
write 

^ 2 r 2 

K +*i + ^ = ^2 + + jjr + h f • • • • ( 2 ^) 

In the figure the line EF y the ordinates to which measured from 
cne pipe represent the pressures in the pipe, is called the hydraulic 
grade-line of the pipe. If the pipe is of uniform size, then v x = v 2 
= v s , etc., whence h x -f- z x = h 2 -j- + h f ; that is, the difference of 

elevation of the hydraulic grade-line at any two points represents the 
head lost in friction between these two points. As the elevation of the 
hydraulic grade-line is independent of the elevation of the pipe, it is 
convenient to refer directly to the datum plane and to write H x — H 2 
h f . If the pipe lies above the hydraulic grade-line at any point, the 
pressure there will be less than atmospheric and the pipe will act as a 
siphon, provided its elevation above the hydraulic grade-line does not 
exceed the height of the water-barometer as given on page 214. 

The usual problem to be considered in the flow of water through 
pipes is to trace out the various losses of head which take place between 
the water at the reservoir and at any point on a pipe-line, or, in other 
words, the head required ( 77 0 — H x ) to overcome friction between A and 
' 2 ? and to causre a velocity of flow equal to v v The relation is 


H n - H, = 


V * 
1 

2^ 


+ kf* 



NATURE OF FLUID FRICTION . 


227 


Or if between any two points in a pipe, it is 


v n 


v , 


1 2 2 ^ 2 ^* 7 


261. Nature of Fluid Friction.—The resistance to the flow of water 
through pipes may be considered as made up of two parts: (1) that 
due to the friction of water on the inner surface of the pipe,—a function 
of the viscosity of the water; and (2) a loss of energy resulting from 
eddies produced in the water by irregularities in the surface of the pipe. 
Until quite recently the great importance of the second factor has not 
been appreciated. Where water flows through a pipe with a rough inner 
surface, such as a riveted steel pipe, a great disturbance is caused in 
the stream of water, which may extend entirely through the mass; and 
it is the internal work of friction resulting from these eddies, and the 
churning up of the water caused by projecting rivets and plates, that 
constitutes by far the larger portion of the total energy consumed in 
the flow. The total loss of head in a pipe such as here mentioned is 
thus very much greater than that which occurs in a smooth pipe whose 
diameter is equal to the clear diameter of the rough pipe. With very 
rough channels almost the entire loss of head is chargeable to this 
element of internal friction due to eddies. In speaking, therefore, of 
the fluid friction in pipes it is necessary to bear in mind that it is prin¬ 
cipally internal friction, and to a very slight extent a friction of the 
water upon the surface of the channel. 

The relative importance of resistance due to viscosity and that due 
to internal friction depends much upon the velocity of the flow and the 
diameter of the pipe, as well as upon the roughness of the channel. 
For low velocities and small diameters the resistance is largely due to 
viscosity, in which case it varies closely with the velocity. At ordinary 
and high veocities it is due largely to internal friction and varies nearly 
as the square of the velocity. These relations are, however, much 
influenced by the roughness of the channel. 

262. General Formulas.—Owing to the variation in the general law 
due to variation in conditions, as noted in the foregoing article, it is 
impossible to derive a formula which will apply to all cases. The best 
that can be done is to select a form of expression which will approxi¬ 
mately represent the law, and then to make use of coefficients by which 
the results of experiments may be conveniently expressed and utilized. 
The approximate law commonly used is that the loss of head varies 
with the square of the velocity, with the length of the pipe, and 
inversely with its diameter. Variations due to differences in the char 


228 


HYDRA ULICS. 


acter of the surface of the pipe, and deviations from the assumed law 
due to other causes, are taken account of in the coefficient. The form 
of expression employed in theoretical discussions and to some extent 


in practical problems is 


l v l 
J d 2 g 



in which h — loss of head; 

f = friction factor; 
l — length of pipe; 
d — diameter. 

The value of/in this expression is an abstract number, and there¬ 
fore the same for any system of units. Tables giving values of / for 
smooth cast-iron pipes are given in various works on hydraulics; these 
values vary from about .01 for large pipes and high velocities to .03 
for small pipes and low velocities. 

In practice the use of a coefficient f is somewhat inconvenient. A 
more commonly used form of expression, and one which is applied also 
to open channels, is the Chezy formula: 

v = c Vrs, .( 28 ) 


in which r = hydraulic mean radius; 

h 

s — hydraulic slope = y; 


c = a coefficient. 

In the case of a pipe flowing full, r = \d. 

In the above formula the value of c will be different for different 
systems of units. In most cases the foot and second are assumed to 
be used. Note that the coefficient c in this formula is equivalent to 

°f formula (27). Various expressions and values for c have been 

proposed by different investigators for different materials and under 
different conditions. 


263. Coefficients and Formulas for Cast-iron Pipes.—The greatest 
attention has been given to the flow of water through smooth pipes of a 
character similar to new, or nearly new, cast-iron and smooth wrought- 
iron pipes. The most reliable and thorough examination of experiments 
of this character is probably that by Hamilton Smith.* The results of 
his investigation are given in the form of tables and diagrams of values 
of c in the Chezy formula for various velocities and diameters of pipes. 


* Hydraulics. N. Y., 18S6. 





COEFFICIENTS AND FORMULAS FOR CAST-IRON FIFES. 



Fig. 33. —Coefficients for Cast-iron Pipes. (Coffin.) 


0 
























































































































































































































230 


HYDRAULICS. 


The diagram Fig. 33 is taken from Coffin.* It is slightly modi¬ 
fied from the one given by Smith, the dotted lines being interpolated 
by Coffin. This diagram probably represents the best available infor¬ 
mation on the subject, but for large sizes and for very small sizes it 
must be considered as rather uncertain. For practical use also, the 
diagram is somewhat inconvenient, as it will frequently happen that 
both v and c are unknown, the head being the known factor. In this 
case the problem must be solved by making two or three successive 
approximations. 

A formula which has been used extensively for cast-iron pipes is 
the Darcy formula. It is 

v= — . ■ Vrs f .(29) 

V a + 2 

where a and ft have the following values for English units: 

For new cast-iron pipes a = .00007726; ft = .00000647. 

For old or rough iron pipes a = .0001545 ; ft = .00001294. 

It is to be noted that the values of these constants for old pipes are 
taken just double those for new pipes, which results in giving for a 
particular velocity double the loss of head in the former case as in the 
latter. Darcy’s formula was derived from experiments on compara¬ 
tively small pipes, and it is probably true that for large pipes and high 
velocities it gives somewhat too small values for the velocity. Levy 
has modified Darcy’s formula slightly, but the modification is too small 
to be of any practical consequence. 

Instead of using a variable coefficient it has been proposed by some 
to adopt a formula of the form v = cr n s vt . This is in some respects a 
more convenient form of expression than the Chezy formula, and for 
any particular class of pipes it can be made to fit the experiments quite 
as well. Two formulas of this class deserve mention, that of Lamp6 
and that of Flamant. Lampe’s formula is, in English units, 

v = 77.68^ ,694 ^- 55S ,.(30) 

where d — diameter of the pipe and s — slope. Flamant, after making 
a thorough examination of all available experiments, proposes the fol¬ 
lowing formulas: t For cast-iron pipes slightly incrusted, such as would 
nearly always be the case after a few years of service, 

, v — 76.2$d*s% .(31) 


* The Graphical Solution of Hydraulic Problems. New York, 1897, 
f Annales des Ponts et Chaussees, 1892, 11. pp. 301-350. 






COEFFICIENTS AND FORMULAS FOR CAST-IRON PIPES. 23 1 
and for new cast-iron pipes 

v — 86.3 8 d 7 s* .(32) 

Besides the above formulas and sets of coefficients, Kutter’s formula 
for c (given on page 246) is frequently applied to pipes, although 
derived from experiments on open channels. The value of n is taken 
according to the nature of the surface, it being usually assumed about 
.011 for smooth pipes. 

264. Comparison of Various Formulas.—In the following table a 
brief comparison is made of various formulas. 

TABLE NO. 46 . 

COMPARISON OF VARIOUS FORMULAS FOR THE FLOW OF WATER IN SMOOTH PIPES. 


Diam. 

in 

Inches. 

Slope. 

Velocities in Feet per Second. 

Smith. 

Lampd. 

Flamant. 

Darcy. 

K utter. 
n = .011. 

New Pipe. 

Pipes in 
Service. 

New Pipe. 

Rough 

Pipe. 

( 

.004 

I.07 

I.05 

1.02 

O.90 

1.20 

O.85 

O.79 

2 1 

• 05 

4-54 

4-25 

4-34 

3-83 

4.24 

3-00 

2.78 

( 

.20 

9.68 

9.17 

9-59 

8.46 

8.47 

5-99 

5-57 

( 

.OOI 

1.00 

1.04 

1.02 

0.90 

I. 18 

O.83 

0.96 

6 | 

.01 

3-67 

3-73 

3.80 

3-35 

3-72 

2.63 

3-12 

1 

. I 

12.80 

I 3-38 

14-13 

12.47 

H -77 

8.32 

9-85 

( 

.0005 

1.08 

1.14 

1.12 

0.99 

1.22 

0.86 

1.14 

12 ) 

.005 

• 3-0 

4.11 

4.18 

3-69 

3-86 

2-73 

3-73 

( 

.025 

9-56 

10.03 

10.51 

9.27 

8.64 

6.11 

8-35 

( 

.OOOI 

1.01 

1.00 

O.98 

0.87 

0.97 

0.68 

1.06 


• OOI 

3-57 

3.60 

3.66 

3-23 

3-07 

2.17 

3.62 

1 

.OI 

12.60 

12.92 

I3.64 

12.03 

9.72 

6.87 

11.50 

( 

.00005 

1.01 

0.97 

0-95 

0.84 

0.89 

0.63 

1.04 

6cJ 

.0005 

3 - 5 i 

3-49 

3-55 

3-13 

2.82 

1.99 

3-57 

( 

.005 

12.50 

12.54 

13.22 

11.66 

8.92 

6.31 

n -45 


An examination of the table shows that the results by Smith’s 
diagram, by the formula of Lampe, and by Flamant’s formula for new 
pipes all agree very closely. Flamant’s formula for pipes in service 
gives velocities about 10 per cent lower than Smith’s diagram. The 
loss of head would be about 20 per cent higher. Darcy’s formula 
gives, in the case of pipes of large size, results considerably below the 
others. Kutter’s formula, on the other hand, gives relatively low 
results for small pipes. 





























232 


HYDRA ULICS. 


265. Diagram Recommended for Use in the Design of Distributing 
Systems.—Among the various formulas mentioned, that of P lamant 
for cast-iron pipes in service is considered to be the most suitable for 
use in the design of ordinary distributing systems. It gives a slight 
margin of safety, which, in case the pipes are properly coated, will 
probably cover the deterioration for ten or fifteen years. This formula 
has the further advantage of being easily solved by the use of loga¬ 
rithms, and can also be readily solved graphically. The diagram on 
page 233, constructed after the principles laid down by M. Lalanne 
and M. Daries,* is based on this formula. It is very simple and offers, 
little chance for error. On the four vertical lines are shown the four 
quantities, discharge, diameter, loss of head or slope, and velocity. 
The intersections of any straight line with these four vertical lines 
indicate corresponding values of these four quantities; so that any two 
being given, the other two are determined by the application of a. 
straight-edge.f 

In the case of the design of large and important conduits no formula 
should be accepted without question,‘but a special investigation of the 
matter of coefficients should be made. Much aid in estimating values 
for such coefficients will be obtained from the extensive Table No. 1 
of Trautwine’s translation of Ganguillet and Kutter, which contains a 
large collection of data of experiments, and calculated values of c 
and n. 

266. Effect of Age of Service on Loss of Head.—In the diagram 
recommended for use some 10 per cent reduction of velocity, or about 
20 per cent increase in head, has been allowed for slight deterioration 
of the pipe. In some cases this would doubtless be sufficient to cover 
a period of ten or even twenty years, while in other cases it would 
undoubtedly be too small an allowance. Uncoated cast-iron pipe 
becomes very badly tuberculated within ten years or less, and the 
reduction in carrying capacity of such pipe has been shown by experi¬ 
ments to be very great,—75 per cent, or more, in the case of 4- and 
6-inch pipe. Properly coated cast-iron pipe, such as is universally used 
at the present time, corrodes very much less rapidly. Many cases 
have been reported of tar-coated pipe which has remained perfectly 
clean and bright for twenty or thirty years. On the other hand, there 
is ample evidence that tar-coating does not always entirely prevent the 
formation of tubercles. The extent of this action is doubtless influ- 

* Nouvelle Annals de la Construction, Aug. 1897, xliii. 

f See also logarithmic diagram based on Levy’s formula in Eng. News , 1899^ 
XI II. p. 4. 





DIAGRAM FOR CA L C ULA TING CA ST-IR ON PIPES, 


20- 

—9000 

72 — 


.03 — 


—8000 

66 — 


- 


— 


T 

O 

• 


— 7000 

60 — 


— 


— 



•03 


—6000 

54 — 


.06 — 


—5000 

48 — 


.08 ~E 

10- 


42 — 


Ol-f 

9- 

— 4000 




8- 

— 

36 — 


— 

*7 _ 

t 

—3000 

— 


.2 -= 

6H 


30 — 


— 


— 

28 - 


.3 — 

5 — 


26 - 


- 


— 2000 

24 — 


.4 — 

4 — 


22 — 


.5 — 


— 





— 

20- 



c 

0 

— 0 

4_> 

18 — 


.8 -E 
I.O*^ 

0 

c« •= 

53 

^ 2- 

- a 

16 — 

Cfl 


1 | 1 | 1 

CD — 

O O 

O O 

O 

per Mir 

14 — 

<D 

_C 

d 

1 

2 -= 

0 

0J 

—800 » 

12 — 

• 



c 


<u 


0 

—700 - 


CL 
* >—• 

3 — 

X 

5 

— oj 

— 600 ° 

C 

10 — 

9—" 

'ts 

4 — 

c 



L 

5 — 

fl) 

-500 & 

8 — 

CD 

4-) 

<D 

6 — 

&1.0- 

- & 


£ 

— 

S .9- 

0 8 — 
u> 

-400 | 
p 

7- 

d 

Q 

8 — 

P .7- 


6- 


_ 


—300 



— 

.6 — 




— 



5 — 


(20 — 

.5- 

— 



— 


^-200 

4 — 


(30 — 

.4- 




— 





40 — 





50 — 

.3 — 


3- 


60 — 





80 —E 


-100 

- 


100 -^ 


—90 



- 

- 

—80 



— 



2 — 


— 

— 

P-70 



200 — 


—60 



— 


_ 



300 — 


— 50 

L 5 -I 


_ 



400 — 


Fig. 34.— Diagram for Calculating Cast-iron Pipes 


J*0S5 of Head in Feet per 1000 feet 








234 


HYDRA UL1CS 


enced by the quality of the water, but unless the contrary is known it 
will be necessary to assume that more or less incrustation will take 
place. Mr. FitzGerald reports that tar-coated pipe laid in Boston will 
become tuberculated in ten or fifteen years. In some cases consider¬ 
able organic growth has become attached to the interior surface of the 
pipe, and this acts greatly to reduce the carrying capacity. 

Tuberculation or incrustation affects the carrying capacity of a pipe 
in two ways: first, it reduces the cross-section, and, second, it 
increases the roughness of the pipe. The total effect on velocity will 
be very much greater in small pipes than in large pipes. Compara¬ 
tively few reliable experiments have been made on old tar-coated pipes, 
most of the experiments on old pipes being on the uncoated pipe. 
Forbes * found in an eighteen-year-old tar-coated pipe 14 and 16 inches 
in diameter a value of c equal to from 90 to 93, about 25 per cent less 
than for new pipe. Experiments by FitzGerald + on a 48-inch pipe 
sixteen years old (tar-coated) gave a value of c — 108 {11 — .014). 
The value of c for this same pipe when new was 140 to 144. The 
velocity in the old pipe was thus about 24 per cent less than in the new 
pipe. 

Of the various formulas for old pipes, that of Darcy has probably 
been the most frequently used. As already noted, it simply gives twice 
the loss of head, or seven-tenths the velocity, as for new pipe. 
Mr. E. B. Weston suggests a series of coefficients whereby the increase in 
loss of head due to age is placed at about 16 per cent each five years over 
what it is at the beginning, but no allowance is made for differences in 
size of pipe. Coffin has constructed a diagram, based upon experiments 
on old pipes, which gives an increase in loss of head for increase of 
service of 15 to 25 per cent for each five years for ordinary velocities 
of 2 to 5 feet per second. The effect is made greater the greater the 
velocity. Some indication of the effect of age on riveted pipes will be 
found by a study of Table No. 48, page 236. 

267. Friction Loss in Service-pipes. —The diagram on page 233 is 
not suitably arranged for calculating sizes of small pipes such as are 
used for service connections; and furthermore, since service-pipes are 
usually made of lead or of galvanized iron, they are little subject to 
corrosion, and the velocity which might be obtained from the diagram 
would be rather low. For the design of such pipes Smith’s coefficients 
given in the diagram of Fig. 33 will give results sufficiently close for 
all practical purposes, although for pipes less than 1 inch in diameter 


* Jour. New Eng. W. W. Assn., 1892, VI. p. 164. 
f Trans. Am. Soc. C. E., 1896, xxxv. p. 241. 





COEFFICIENTS FOR RIVETED PIPES. 


235 


the results are probably somewhat too low. Table No. 47 is calcu¬ 
lated from these coefficients. For very smooth pipes, such as those of 
lead or brass, Mr. E. B. Weston proposes the following formula for 
the friction factor /of eq. (27): 


f= 0.0126 -f- 


0.0315 — 0.0 6 d 

V v 



In which the foot-unit is to be used. Tables based on this formula are 
given in Weston’s “ Friction of Water in Pipes.” This formula gives 
velocities somewhat greater than Smith’s coefficients. 


TABLE NO. 47 . 

LOSS OF HEAD IN SMALL PIPES. 


Velocity, Ft. per Sec. 

Pinch Diam. 

i-inch Diam. 

iPinch Diam. 

2-inch Diam. 

2pinch Diam. 

3-inch Diam. 

Discharge, 
Gallons 
per Min. 

Loss of Head, 
Feet 

per 100 Feet. 

Discharge, 
Gallons 
per Min. 

Loss of Head, 
Feet 

per 100 Feet. 

Discharge, 
Gallons 
per Min. 

Loss of Head, 
Feet 

per 100 Feet. 

Discharge, 
Gallons 
per Min. 

Loss of Head, 
Feet 

per 100 Feet. 

Discharge, 
Gallons 
per Min. 

Loss of Head, 
Feet 

per 100 Feet. 

Discharge, 

Gallons, 
per Min. 

Loss of Head, 

Feet 

per ioq Feet. 

I 



2. 5 

.82 



9 . 8 

• 35 

15-3 

• 27 

22.1 

. 22 

I * 



t .. 7 

I .61 

8.2 

I .Ol 

I4.7 

.72 

J J 

23.O 

• 56 

33 • I 


A 2 

2 



J * / 

A . Q 

2 . 63 

11 . 0 

1.67 

iq. 6 

1 . 19 

30.7 

. 02 

Ad . 2 

* 76 

2 h 

1-53 

10.00 

*T * V 

6.1 

387 

13.8 

2-44 

24-5 

1-73 

38.3 

1.36 

55-2 

I . IZ 

3 

I.84 

14.2 

7-4 

5-33 

16.6 

3-37 

29.4 

2-39 

46.0 

1.88 

66.2 

1 • 55 

3l 

2 .15 

17-7 

8.6 

6-95 

19-3 

4.44 

34-3 

3 -i 4 

53-7 

2.47 

77-3 

2.02 

4 

2.45 

22.4 

q.8 

9 - 3 i 

22.1 

5-56 

39-2 

3-98 

61.3 

3-13 

88.3 

2.56 

4* 

2.76 

27.6 

II .0 

10.9 

24.8 

6.89 

44.1 

4.91 

69.0 

3.85 

99.4 

3 -i 4 

5 

3.06 

33-3 

12.3 

12.3 

27.6 

8-33 

49.1 

5 94 

76.7 

4.66 

no. 4 

3.81 

5 ^ 

3-37 

39-7 

13-5 

15-5 

30-4 

9.88 

53-9 

6.42 

84-3 

5-53 

121.4 

4-52 

6 

3.68 

46.7 

14.7 

18 . 2 

33 -i 

11 .5 

58.8 

8.22 

92.0 

6-45 

132.5 

5-27 

6* 

3-98 

54-2 

15-9 

2 0.9 

35-9 

13-3 

63.8 

9 - 5 i 

99.6 

7.46 

143-5 

6.10 

7 

4.29 

62.6 

17.2 

24.0 

38.6 

15-2 

68.6 

10.8 

107.3 

8-53 

154.6 

7.01 

7h 

4.60 

7 i .3 

18.4 

28.9 

41.4 

17.3 

73-6 

12.4 

115.0 

9.70 

165.6 

7-93 

8 

4.90 

80. 8 

19.6 

32-7 

4.J.2 

19-5 

78.5 

13-9 

122.6 

TO. 9 

176.6 

8-94 

8\ 

5-21 

90.6 

2C-9 

36.9 

46.9 

21.9 

83-4 

15.6 

130.3 

12.2 

187.7 

10.00 

9 

5 - 5 i 

101.6 

22. I 

41.2 

49-7 

24.4 

88.3 

17-3 

138.0 

13.6 

198.7 

11 . 1 

9^ 

5.S2 

112.9 

23-3 

45-9 

52.5 

27.2 

93-2 

19-3 

145.6 

15 .I 

209.7 

12.3 

10 

6.13 

124.8 

24-5 

48.0 

55-2 

30.2 

98.1 

21.3 

153-3 

l6.6 

220.8 

13-7 


268. Coefficients for Riveted Pipes. —The friction loss in riveted pipes 
depends upon the thickness of the plates and the manner of making 
the joints. Experiments on this class of pipes are not sufficiently 
numerous to enable any general expression to be formulated, so that 
in the design of such pipes the selection of coefficients must be made 
by reference to the experimental data. In general it is found that the 
coefficient c changes little with change in diameter or velocity, and in 
this respect exhibits considerable difference from its variation in cast- 














































236 


HYDRA ULICS. 


iron pipe. For ordinary velocities the value of c for new pipe appears 
to range between 100 and 115. Probably a value of no would be as 
great as should be used in almost any case. Kutter’s formula for c is 
very often used, the value of n being taken equal to .013 to .015. 

To aid in the selection of a coefficient, all the most important 
experiments on large riveted pipe are given in Table No. 48. Further 
data regarding these experiments will be found in the various publica¬ 
tions referred .to. The table is mostly taken from a similar one given 
in the paper by Profs. Marx, Wing, and Hoskins in Trans. Am. Soc. 
C. E., 1898, vol. XL. p. 471. 

TABLE NO. 48 . 


VALUES OF THE COEFFICIENT C FOR RIVETED PIPES. 



V 

a 

(X 





Velocities 

in Feet per Second. 


















•N-« % 

0 a 

u U 

<v a; 
jo a 

, v 

"u 

«L> C 

a 

1.0 

*.5 

2.0 

2-5 

3° 

3-5 

4.0 

4-5 

5-0 

5-5 

6.0 

a * 

1 

X C 

q'“ 

Values of Coefficient c. 

1 

II 

14 

15 

16 

9/1 








107. I 



no .6 

2 

•2 

87 

• 






t t r . f\ 


J 

A 








T TO n* 




5 

6 






78.5* 












T Ol O* 





7 

JJ 

35 

36 
36 
33 
33 
42 
42 
42 
48 
48 
48 
48 
72 
72 

103 






126.8* 
107.0 

1 ^ ^ . -w 





8 

Q 

86 

90.8 

95 

2 

99.4 

103.3 

no.6 

II4.O 

II7.2 

106. 3* 

120.4 

123.6 

10 

11 






Il6.6* 










J HQ 2 * 





12 

13 

14 

15 

16 

17 

18 

19 

20 

21 




11 5 • 9 * 
in .0 

105.5 

in.2 
92.4 
104.9 

101.6 
108 
101.3 
108.8 








96.0 

101.0 

IOT . 2 
78.0 
97.2 
97.1 

no 

81.6 

116.6 

103.0 

102.8 

T05.4 

84.6 
100.8 

98.7 
in 

92.0 
112.7 

107 
104 

108 
89 

103 

100 

no 

98 

no 

9 

3 

8 

6 

3 

3 

0 

3 

112.6 
106.4 
112.8 

93 -o 

105.3 

102.2 
108 

102.4 

107.7 

113-0 

107.2 
II 3-4 

93*2 

104.8 
103.6 

JIO 

103.2 

106.9 

112.8 

107.8 

113.2 
94.O 

IO4.O 

104.2 
III 

103.8 

106.2 

III.8 

105.2 
112.4 

94.2 

103.7 

104.7 

104.3 
IO5.6 

no. 8 
108.4 
112.0 
94.4 

103.7 
105.1 

104.7 

no. 2 
108.5 
in. 7 
94.7 

103-7 

105.2 

105.0 

no.o 
108.5 
in .6 
94.9 
103.7 
105.2 


* Most of the values in the table were obtained from plotted curves. Those 
marked with an asterisk are from single observations and are inserted in the table 
under the velocity corresponding most nearly with the observed velocity. 


The following is a brief description of the experiments the results of 
which are tabulated above: 

Nos. 1 and 3 . By Hamilton Smith, North Bloomfield, Cal. Sheet iron 
with taper joints; asphalt and tar-coating; 5 years old. 

No. 2 . By A. McL. Hawks. Cylinder-joints; asphalt coating. Tested 
when 3 years old, and also when 6 years old with same results. Trans. Am. 
Soc. C. E., 1899 , XLIL P- I 55* 






















































FRICTION LOSS IN IVOOD-STA VE PIPE. 237 

No. 4. By A. L. Adams. Astoria pipe-line. Cylinder-joints; asphalt 
coating; new pipe. Trans. Am. Soc. C. E., 1896 , xxxv. p. 226 . 

No. 5 . By Geo. W. Rafter on the old Rochester conduit. Cylinder- 
joints; 14 years old. Trans. Am. Soc. C. E., 1891 , xxvi. p. 20 . 

Nos. 6 , 7 , and 12 . By. I. W. Smith on the Portland conduit. Cylinder- 
joints; asphalt coating; new pipe. Trans. Am. Soc. C. E., 1891 , xxvi. 
p. 203 . 

Nos. 8 and 9 . By Clemens Herschel on the conduit of the East Jersey 
Water Company from Belleville to South Orange. No. 8 made with new 
pipe; No. 9 with pipe 4 years old. Cylinder-joints; asphalt coating. 
Herschel’s “115 Experiments.” 

Nos. 10 and 11 . By Kuichling on different sections of the Rochester 
conduit. Cylinder-joints. The section of pipe in experiment No. 10 was 
coated partially with asphalt and partially with the Sabin coating. Average 
plate thickness = .27 inch. Section in experiment No. n coated with Sabin 
coating; average plate thickness .31 inch. Age of pipes about i4 years. 
These same sections gave in November and December, 1898 , coefficients of 
112.9 and 105.9 respectively. Annual Reports of Executive Board of 
Rochester, 1895 - 98 . 

Nos. 13 to 18 . Experiments by Herschel. No. 13 , Kearney extension 
of the East Jersey Water Company’s pipe-line. Taper joints; new pipe; 
coating “ unusually smooth.” No. 14 , on conduit No. 2 of the East Jersey 
Water Company; new pipe. No. 15 , on conduit No. 1 ; cylinder-joints; 
asphalt coating; new pipe. Nos. 16 and 17 , on portions of the same conduit 
as No. 15 , but 4 years later. No. 18 , on portion of conduit No. 2 ; taper 
joints; new pipe. “ 115 Experiments.” 

No. 19 . 'Experiments by Marx, Wing, and Hoskins on the conduit of 
the Pioneer Electric Company, Ogden. New pipe; butt-joints; asphalt 
coating. Trans. Am. Soc. C. E., 1898 , xl. p. 471 . 

No. 20 . Same as No.. 19 , but 2 years later. Proc. Am. Soc. C. E., 
Feb. 1900 , p. 108 . 

No. 21 . By Herschel on Holyoke flume. Cylinder-joints; paint coating 
washed off; rather rusty. “115 Experiments.” 

269. Friction Loss in Wood-stave Pipe.—Very few experiments have 
been made on this class of pipes. Such information as is available is 
collected in the paper by Marx, Wing, and Hoskins, already referred 
to, in which are also described some experiments by the authors on the 
Ogden 72-inch wooden-pipe line. The few experiments made previous 
to these indicated a value of n in Rutter’s formula of about .010 for 
18- to 30-inch pipes. The experiments on the Ogden pipe-line, how¬ 
ever, gave a value of c varying from 100 to 125 for velocities varying 
from 1 to 4 feet per second. This value of c corresponds to values of 
n varying from .015 to .0128. Experiments on this same pipe-line in 
1899 (two years later) gave a very uniform value of the coefficient c 
of 118 to 122, corresponding closely to a value of n equal to .013. 

270. Measurement of Flow through Large Pipes.—The quantity of 
water flowing through pipes may be measured by means of weirs or 


238 


HYDRAULICS. 


orifices, or by noting the rate of filling of a reservoir, or by the use of 
meters. In Chapter XXIX various kinds of meters are described 
and discussed with particular reference to their use on service-pipes. 
For accurately measuring the quantity of water flowing through large 
pipes, as in the making of tests, probably the best form of meter is the 
Venturi. This meter simply consists of a contracted section of pipe, 
AB, Fig. 35, with pressure-gauges at A and C. If v x and v 2 are the 



velocities at A and C , h x and h 2 the pressures, a x and a 2 the areas, 
then, neglecting friction, we have, from eq. (26), page 226, 


zA 

h x + -±- = k 2 + -^~ 

1 1 2g 2 2g 


( 34 ) 


But if Q — theoretical discharge, then v, = — and v„ = —. 

<*2, 

Substituting and reducing, we have 



a x a 2 _ 

VgLa} V2 £t*i - K)- 



If q = actual discharge, then q — cQ, where r is a coefficient deter¬ 
mined by experiment and nearly equal to unity.* 

271. Minor Losses of Head. —Loss of Head at Entrance. —This is 
expressed by the formula 



( 36 ) 


where v = velocity in the pipe, and c is the coefficient of discharge of 
a short tube having the same form as the end of the pipe. For various 


forms at entrance we have the following 

values: 


T 

Pipe projecting into reservoir 

c. 

. . .;2 


7 2 ~ J ' 

•93 

End of pipe flush with reservoir. 

. . .82 


•49 

Conical or bell-shaped mouth 

. . .93 to 

.98 

.15 to .04 

* See paper by Herschel on Venturi Meter, 

Trans. Am. 

Soc. 

C. E., 1887, xvn ( 


p. 228. 


XVII. 





















MINOR LOSSES OF HEAD. 239 

272. Loss Due to Sudden Enlargement. —This is given by the 
formula 

/ t a 2 \ 2 

k ~ 0 i* . f37) 

in which a 1 and a 2 are the cross-sections of the smaller and larger pipes 
respectively, and v 2 is the velocity in the larger pipe. 

273. Loss Due to Sudde?i Contraction. —This is given by 

/i fv 2 

* = \7~ l )T g .(3 8 ) 

in which c r depends on the ratio of the two diameters and is given by 
Merriman as follows: 

Ratio of smaller to larger diameter. .. . o .2 .4 .6 .8 1.0 

c' .62 .63 .64 .67 .72 1.a 

274. Loss of Head at Bends is equal to 

h = f g .(39) 

for a 90° bend, in which 71 has the following values according to the 
ratio of the radius of the pipe r to the radius of curvature R 
(We is bach): 

r 

ji[ . 1 * 2 *3 -4 *5 -6 .7 *8 .9 1.0 

n .13 -14 -i6 ,2i .29 .44 .66 .98 1.41 1.98 

275. Loss of Head in Valves. —Weisbach’s experiments on small 

gate-valves gave values for n in the expression h = n — as follows* 

2 g 

Ratio of height of opening to diameter. f- J \ | 

Values of n .07 .26 .81 2.1 5.5 1798 

In applying the above formula v is the velocity in the pipe. 

For a throttle-valve placed at various angles 6 with the axis of the 
pipe, Weisbach found the following values of n : 

6 ... 5 0 io° 20 0 30° 40° 50° 6o° 65° 70° 

n... .24 .52 1.5 3.9 11 33 118 256 750 

Experiments on large gate-valves have been made by Kuichling 
and by J. W. Smith. The following table gives values of the coefficient 

c in the expression Q — cA V2gh as deduced by Kuichling from these 
two sets of experiments.* In this expression A is the area of the 
opening, h is the head lost in the valve, Q is the rate of discharge. 


* Trans. Am.Soc. C. E., 1895, xxxiv. p. 243. 










240 


HYDRA ULICS. 


TABLE NO. 49 . 


COEFFICIENTS 

FOR 

LARGE 

GATE-VALVES. 





Ratio of height of opening j 
to diameter j 


.05 

.1 

.2 .3 

•4 

• 5 

.6 

• 7 

.8 

Ratio of area of opening 
to total area 

f . 

.05 

.IO 

.23 .36 

.48 

.60 

• 7i 

.81 

.89 

Coefficient c for 24-inch valve. 

1-7 

1.0 

.72 .70 

•77 

.92 

1.2 

1.6 


Coefficient c for 30-inch valve. 

1.2 

•9 

.83 .82 

.84 

.90 

1.05 

i-35 

2.1 

Experiments at the Ohio State University in 

1899 on 

various ' 

kinds 


of small valves showed that gate-valves when wide open gave a coeffi¬ 
cient of discharge equal to from .5 to .7, and globe-valves usually from 
.3 to .4.* 

276. Hydraulics of Fire-streams.—Table No. 50 contains data per¬ 
taining to the loss of head in fire-hose, and the character of fire-streams 
under different pressures and for different-sized nozzles. The data are 
taken from much more extensive tables given by Freeman in his 
elaborate paper on the hydraulics of fire-streams. + 

TABLE NO. 50 . 

HOSE AND FIRE-STREAM DATA. 


<L> 

IT. 

a 

CQ 

v 

N 

O 

rt O. 
o O- 
3 >, 

V CL 
u 

Oh 

lbs. 


20 

30 

40 

50 

60 

70 

80 

90 

IOO 


i-inch Smooth Nozzle. 

I 

J-inch Smooth Nozzle. 

15 -inch Smooth Nozzle. 

Discharge in Gallons 
per Minute. 

— Loss of Head per 100 

5f Feet of Ordinary 
Hose. 

Vertical Height of Jet 

P for Good Fire- 
streams. 

Maximum Horizontal 
p Distance for Good 
Fire-streams. 

Extreme Drops at 

F Level of Nozzle. 

Discharge in Gallons 
per Minute. 

— Loss of Head per 100 

S’ Feet of Ordinary 

Hose. 

Vertical Height of 

P Jet for Good Fire- 
streams. 

Maximum Horizontal 

P Distance for Good 
Fire-streams. 

-s Extreme Drops at 

F Level of Nozzle. 

Discharge in Gallons 
per Minute. 

_ Loss of Head per 100 

S’ Feet of Ordinary 
Hose. 

Vertical Height of 
p Jet for Good Fire- 
streams. 

Maximum Horizontal 

P Distance for Good 
Fire-streams. 

Extreme Drops at 
Level of Nozzle. 

1 

132 

5 

35 

37 

77 

168 

8 

36 

38 

80 

209 

12 

37 

40 

83 

l 6 l 

7 

5i 

47 

109 

206 

12 

52 

50 

115 

256 

19 

53 

54 

119 

186 

10 

64 

55 

133 

238 

16 

65 

59 

142 

296 

25 

67 

63 

148 

208 

12 

73 

61 

152 

266 

20 

75 

66 

162 

331 

31 

77 

70 

169 

228 

15 

79 

67 

167 

291 

24 

83 

72 

178 

363 

37 

85 

76 

186 

246 

17 

85 

72 

179 

314 

28 

88 

77 

I 91 

392 

43 

9i 

8 l 

200 

263 

20 

89 

76 

189 

336 

32 

92 

81 

203 

419 

49 

95 

85 

213 

279 

22 

92 

80 

197 

356 

36 

96 

85 

214 

444 

55 

99 

90 

225 

295 

25 

96 

83 

205 

376 

40 

99 

89 

224 

468 

62 

IOI 

93 

236 


The range and quality of fire-streams has recently been studied by 
photography by Prof. Marston. His results for i-inch and i-J-inch 
smooth nozzles are shown in the diagrams on page 241. The paths 


* Eng. Record , 1899, XL. p. 78. 
f Trans. Am. Soc. C. E., 1889, xxi. p. 303. 


















































HYDRAULICS OF FIRE-STREAMS, 


241 


Pressure per Sq. In. at Base of Play Pipe 
Pressure 'lo* Pressure 20* Pressure 30 * 



Pressure per Sq. In. at Base of Play Pipe 



I - INCH SMOOTH NOZZLE. 

/ Extreme Drops a 
Freeman's Experiments Plotted thus A Pair Fire Stream. * 

( fivad Fire Stream. <*► 

Fig. 36.—Fire-stream Diagrams. 

(From Engineering Record, Feb. 18, 1899.) 





































































































































































































































































































































































































































































































































































































































242 


HYDRA ULICS. 


of the streams are shaded for pressures of 30 pounds or above, 
wherever a solid stream was shown by the negative. Beyond the 
limits indicated, the slightest breeze would break up the stream badly. 
The results of Freeman’s experiments are also given on the diagrams. 
The pressures in Marston’s experiments were measured at the base of 
the play-pipe, and varied from the effective pressure at the orifice from 
—11 to -j- 1.7 pounds per square inch. Experiments were also made 
on smooth nozzles of f- and £-inch, and on ring nozzles of i-inch and 
ij-inch diameter. The ring nozzles gave, in general, streams of 
slightly less range than the smooth nozzles. 

277. Friction Loss in Fire-hydrants.—Experiments by M. C. L. 
Newcomb at Holyoke, Mass., on twenty-one different kinds of hydrants 
showed that with a discharge of 500 gallons per minute the loss of head 
was in nearly all cases between 1 and 2 pounds per square inch, the 
maximum being 2.5 pounds, and the minimum .8 pound. In many 
cases the greater portion of the loss of head occurred in the nozzle and 
shows the necessity of making the passages in hydrants of large size 
and in curved lines.* 

278. Water-hammer.—When a volume of water flowing in a pipe 
has its velocity rapidly checked by the closing of a valve or otherwise, 
a pressure is developed in excess of the static pressure. If the action 
is very sudden, the pressure will be very great, particularly if the 
velocity is high and the pipe of great length. This effect in general is 
called water-hammer. 

The estimation of the amount of excess pressure due to water- 
hammer in a pipe system is a matter of difficulty, but all engineers 
admit that some allowance must be made. Where the conditions are 
definitely known, such as the size and length of pipe, and the rate and 
manner of closing a valve, it is quite possible to compute the pressure 
with a considerable degree of accuracy. The actual problem is, how¬ 
ever, greatly complicated, due partially to the irregularity in form and 
arrangement of the pipes, but chiefly to a lack of exact knowledge with 
respect to the movement of the valves, pump-plungers, or whatever 
may be the cause of the trouble. It is, however, possible to gain from 
theoretical considerations, and from experiments, a knowledge of 
certain general laws with respect to water-hammer, and to indicate 
certain limits to the pressure which may be produced by it. The 
results of special experiments carried out under certain given conditions 
may also be studied with advantage. 

279. Theoretical Considerations .—The greatest possible water- 


* Trans. Am. Soc. M. E., 1899, xx. p. 494. 



WA TER-IIA AIMER. 


243 


hammer will be caused in any particular case when a valve is closed 
so quickly as to be practically instantaneous. In this case the resulting 
pressure is a function involving the elasticity of the water and of the 
pipe, and is a case of impact of an elastic prism. If the elasticity of 
the pipe be neglected, which may be done for ordinary sizes, the pres¬ 
sure of impact has been shown to be 

vR 

p=-f- .( 40 ) 


in which v = initial velocity of water; 

E w = modulus of elasticity of water 

= 300,000 pounds per square inch; and 
V = about 4700 ft. per second, = velocity of sound in water. 
Substituting the values of E w and V, we have, in pounds per square 
inch, where v is in feet per second, 


p = 64V .(41) 

The pressure developed is thus proportional to the velocity of the 
water and is independent of the length of the pipe. 

Mr. Frizell * has derived the following expression for the pressure, 
in which account is taken of the elasticity of the pipe: 


v 



1 + 


2r EJ * 
t ' E P 


• , (42) 


in which E P — modulus of elasticity of pipe; 

2 r — diameter of pipe in feet; and 
t — thickness of pipe in inches. 

These formulas are valuable as indicating the maximum possible 
limit of the water-hammer. The question arises, however, as to what 
constitutes a sudden stoppage of the water. According to Mr. Frizell 
the closing of a valve is essentially instantaneous if the time of closing 
is less than the time necessary for the wave of pressure to be trans¬ 
mitted to the end of the pipe and back, at the rate of about 4700 feet 
per second. The length of pipe is thus seen to enter into the problem 
of water-hammer by affecting the definition of the word ‘sudden.’ In 
long pipes, therefore, the operation of the valves in a way similar to 
that customary for short pipes would be likely to cause a much greater 
water-hammer; and in very long pipes a severe hammer might be 
experienced even though the operation were relatively slow. 

The other case to be considered, the one in which the stoppage of 
the flow is not sudden, is the more usual problem, but at the same time 


* Trans. Am. Soc. C. E., 1898, xxxix. p. 1. 










244 


HYDRA UL1CS. 


one more difficult of treatment. The pressure developed in this case 
is simply a function of retardation and of the static head; and if the 
manner of operating a valve is precisely known, the pressure can be 
computed. If a valve is closed at a uniform rate, the pressure will be 
a maximum at the end of the movement, and with similar laws of 
closing the pressure will be approximately proportional to the length 
of the pipe, to the speed of closing of the valve, and to the velocity of 
the flow. A lower maximum pressure will be experienced if valves 
are so arranged as to close rapidly during the first part of the move¬ 
ment and slowly at the last.” 

280. Experiments on Water-hammer. —Experiments on water-ram 
have usually been made by determining the pressures developed in 
certain short lines of pipe by the sudden closing of a gate-valve, the 
pressure being measured by means of a gauge. Experiments by Mr. 
E. B. Weston at Providence, R. I.,t on small pipes, by the method 
described, gave results which approached well towards the theoretical 
maximum given by eq. (40). The ram was practically proportional 
to the velocity of the water. 

Experiments by Prof. Carpenter on 2-inch pipes gave results which 
are shown in the diagram of Fig. ^7 .\ The curve for the experiments 
without air-chamber shows values of pressure from one-half to two- 
thirds of those obtained by the use of Mr. Frizell’s formula, eq. (42). 
The pressure here appears to increase somewhat more rapidly than the 
velocity. The effect of air-chambers is very marked. 

Experiments at Dartmouth College in 1898 § indicated that the 
force of water-ram varies with the velocity, with the speed of the clos¬ 
ing of the valve, and with the volume of water in the pipe. It is also 
greater when dead ends are located near the valve. Extensive experi¬ 
ments have been carried out still more recently in Russia, the results 
of which go to confirm the general laws expressed by the formulas of 
Art. 279. These experiments have also led to the general statement 
that the pressure caused by a sudden decrease in velocity is, for each 
foot per second of such decrease, approximately 4 atmospheres (60 
pounds per square inch) for small pipes and 3 atmospheres (45 pounds 
per square inch) for large pipes.|| These values are very nearly the 
same as would be obtained from eq. (42). 


* For a theoretical discussion of the pressures developed when valves are closed 
slowly, together with results of some experiments with slowly moving valves, see 
Trans. Assn. C. E. of Cornell University, 1898, p. 31. See also a paper by Prof. 
I. P. Church in the Journal of the Franklin Inst., April and May, 1890. 
f Trans. Am. Soc. C. E., 1885, xiv. p. 238. 

X Trans. Am. Soc. M. E., 1894, xv. p. 510. Eng. Record , 1894, xxx. p. 173. 

^ Eng . A r e 7 vs, 1898, xxxix. p. 186. || Eng. News, 1900, xliv. p. 80. 




WA TER-HA MMER. 


245 


281. Practical Conclusions .—From the foregoing discussion the 
extreme limits of water-hammer are approximately indicated, and it 
would appear that the general laws are to some extent quite definitely 
known, from both theoretical and experimental considerations. In 
simple cases of the operation of valves it is easy to determine from 
these considerations what are the necessary precautions to be taken. In 
many cases in practice the difficulty arises from causes not easily traced, 
and undoubtedly the effect of hammer is often greatly increased by the 
setting up of vibrations due to some synchronous action of the pumps 
or other machinery, accompanied by the collection of air in the pipes. 



Fig. 37. —Experiments on Water-ram by Carpenter. 

To prevent excessive water-hammer from the closing of valves it 
is only necessary so to design them that they cannot be closed very 
suddenly, or if they are closed suddenly they should be so arranged 
that the velocity in the adjacent main shall not exceed a moderate limit 
of 8 to 12 inches per second at the time when the valve is operated. 
If the velocity at this point were as great as 1 foot per second, the 
maximum possible hammer would be something less than 64 pounds 
per square inch, according to eq. (42). The operation of ordinary 
valves in a distributing system can scarcely give so great a ram as the 
above. Air-valves and pressure-relief valves should be so proportioned 
that any sudden reduction of velocity caused in filling or operating 
a pipe-line shall not exceed a moderate limit such as above speci¬ 
fied. The closing of hydrant-valves would have an effect depending 
upon the amount by which the velocity of water in the adjacent main is 










































HYDRA ULICS. 



influenced thereby. Hydrants attached to small mains will thus have 
a greater effect than when attached to large ones. In the operation 
of long pipe-lines at high velocities, such as are used in power plants 
on the Pacific coast, special precautions must be taken to insure a very 
slow movement of the valves; and frequent use made of air-chambers 
and relief-valves. It has been found that to check the pulsations which 
are caused by the waves of pressure set up, it is advantageous to use air- 
chambers which are single-acting, that is, those which permit water to 
enter readily but not to flow out rapidly. In a distributing system, water- 
ram is sometimes caused by the action of the pumps, due usually to a 
lack of capacity in the air-chambers, or to their becoming filled with 
water. The effect of such ram upon the neighboring pipes is frequently 
influenced by the presence of dead ends, and in some cases trouble of this 
sort has been removed by connecting up two or more such dead ends. 


FLOW OF WATER IN OPEN CHANNELS. 

282. Formulas Employed.—In calculating the flow of water in open 
channels the Chezy formula (page 228) is used. It is 

v — c Vrs y 

in which r = hydraulic mean radius; 

s — sine of the slope of the water-surface; 
c — a coefficient. 

For channels similar in character to smooth pipe the value of c may 
be taken from page 231. 

The most commonly used value of c is that given by Kutter’s 
formula, which was derived from a study of a large number of experi¬ 
ments. It is, 


1.81 0.0028 

+ 4 i -65 -|--— 


c = 


n 


[ 0.0028\ 

d 4I - 6 5 H- 7 -) 


( 43 ) 


I + 


V r 


in which n is a coefficient of roughness. The following are the values 
of n usually assumed for the various surfaces mentioned: n 

Channels of well-planed timber.009 

“ neat cement or of very smooth pipe.010 

“ unplaned timber or ordinary pipe.012 

“ smooth ashlar masonry or brickwork.013 

“ ordinary brickwork.015 

“ rubble masonry.017 

in earth free from obstructions . ....020 to .025 

with detritus or aquatic plants.030 

















FLOW OF WATER IN OPEN CHANNELS. 


247 


In formula (43) it is seen that the value of c is made to vary with 
r and also with s, but the effect of a change in s for all but those cases 
in which the slope is very small is of little importance, and for all prac¬ 
tical purposes in the design of sewers and water-conduits a constant 
value of s, such as .001, may be assumed. Table No. 51 gives values 
of c, corresponding to various values of r and of n, for a constant value 
of s equal to .001. 


TABLE NO. 51 . 

VALUES OF C IN KUTTER’s FORMULA WHEN S = 0 . 001 . 


Values of n. 


r in 


Feet. 

.009 

.OIO 

.Oil 

.012 

.013 

.015 

.017 

.020 

.025 

.030 

. I 

108 

94 

82 

73 

65 

53 

45 

35 

26 

20 

.2 

129 

113 

100 

89 

80 

66 

56 

45 

34 

26 

•3 

142 

124 

hi 

99 

90 

75 

63 

52 

38 

3 ° 

•4 

150 

132 

118 

106 

96 

80 

69 

56 

42 

34 

•5 

157 

139 

] 24 

hi 

101 

85 

73 

60 

45 

36 

.6 

162 

143 

128 

116 

ic 5 

89 

76 

63 

48 

38 

•7 

166 

147 

132 

119 

109 

92 

79 

65 

50 

40 

.8 

170 

151 

135 

122 

112 

95 

82 

68 

52 

42 

• 9 

173 

154 

138 

125 

114 

97 

84 

70 

54 

43 

I.o 

175 

156 

140 

127 

116 

99 

86 

7 i 

55 

45 

1.2 

180 

160 

145 

131 

120 

103 

89 

74 

58 

47 

1.4 

184 

164 

148 

135 

124 

106 

92 

77 

60 

49 

1.6 

187 

167 

151 

137 

126 

108 

94 

79 

62 

5 i 

1.8 

189 

169 

153 

140 

129 

no 

97 

81 

64 

53 ' 

2.0 

191 

172 

155 

142 

130 

112 

98 

83 

65 

54 - 

2.5 

196 

176 

160 

146 

135 

116 

102 

86 

69 

57 ' 

3-o 

199 

179 

163 

149 

138 

119 

105 

89 

7 i 

59 

3-5 

202 

182 

166 

152 

140 

122 

107 

9 i 

73 

6r 

4.0 

204 

184 

168 

154 

143 

124 

no 

93 

75 

63 

4*5 

206 

186 

170 

156 

144 

126 

in 

95 

77 

64 

5-o 

208 

188 

172 

158 

146 

127 

113 

97 

78 

66 


Values of c from gaugings of the New Croton Aqueduct and of the 
Sudbury Aqueduct are represented in Fig. 38A The conduits are of- 
horseshoe shape and are brick-lined. In the figure, Kutter’s formula; 
is also plotted for values of 11 equal to .013 and .014* It is to be noted 
that this formula gives values of c, as compared with the experiments, 
which increase too rapidly with increase in r. 

The adopted curve for the Stony Brook conduit is also given. The 

equation of this curve is c — 122.6r°- 57 Vs. The flow in the new Croton 
Aqueduct is closely represented by the equation v = 124;- 56 Vs.f 


* Eng . News, 189S, XL. p. 11. 
f Eng . Record, 1895, XXXII. p. 223. 







































248 


HYDRAULICS . 


283, Measurement of Water Flowing in Open Channels. —In the case 
of small channels the discharge can be measured by means of a weir 
specially constructed for the purpose, which should comply with the 
conditions already noted on page 218. The discharge of large streams 
may often be obtained by noting the head on some existing dam or 
weir. Where such a structure does not exist, then the discharge may 
be found by measuring the cross-section at a suitable place and deter¬ 
mining the average velocity of the water by the use of floats or by a 



current-meter. The latter method is the most reliable. Determina¬ 
tions of discharge having been made at various stages of water, a dis¬ 
charge-curve can be drawn and subsequent values deduced from gauge 
records. Reliable work of this kind involves the consideration of many 
details which cannot be entered upon here and for which reference 
must be had to works on hydraulics and surveying. 

Note.- —The preceding chapter being but a very brief abstract of the more 
•common formulas of hydraulics and of the results of experiments, no attempt 
is made to give a bibliography of the subject farther than is done by the foot¬ 
notes throughout the chapter. These, however, will enable the student to 
refer to much of the most recent information on the subject. For further 
guide, reference should be made to such special works as Hamilton Smith, 
and Ganguillet and Ivutter, and to the various general works on hydraulics. 






































A. WORKS FOR THE COLLECTION OF WATER. : 


CHAPTER XIII. 

RIVER AND LAKE INTAKES. 

284. General Conditions. —In drawing a water-supply from a natural 
body of water there are certain general requirements which the intake 
works are designed to meet. First in importance is reliability of 
operation, as a failure here often means the immediate shutting off of 
the entire supply. Another important requirement is that the point of 
intake should be so located as to obtain water of the best available 
quality. Provision should also be made for excluding fish, various 
floating objects, and the coarser sediment, such as sand and gravel. 
Finally, the construction should be an economical one. 

Intake works consist of some form of conduit (pipe or tunnel) 
extending out to the selected point of intake, some protective works at 
the open end of same, and, usually, regulating-valves and screens placed 
at some point between the pumps and intake. If the intake-pipe is 
short, it may be merely an extension of the suction-pipe of the pumps; 
but where it is long, the usual practice is to interpose a wet-well or 
chamber as near the pumps as practicable and draw therefrom, long 
suction-pipes being disadvantageous. 

Varying natural conditions give rise to important variations in 
arrangement and form of structures, and these will now be briefly dis¬ 
cussed. 

RIVER INTAKES. 

285* Location. —The location of the intake must be selected with 
reference to (1) the quality of the water, and (2) the cost of construc¬ 
tion and maintenance of the works connected therewith in so far as this 
is affected by the question of site. As regards quality the question of 
the effect of the pollution from other cities and towns higher up along 
the stream, and the question of the general suitability of the source, are 
here supposed to have been already considered and a conclusion 

249 


250 


RIVER AND LAKE INTAKES. 


reached in accordance with the principles discussed in preceding- 
chapters. It is equally important that the precise point of location of 
the intake be decided upon with as careful consideration of these prin¬ 
ciples. 

The point of intake should, first of all, be free from local sources 
of pollution and should therefore be located above all sewer outfalls of 
the town in question. In the case of tidal streams, sewage-po.lluted 
water may be carried long distances above the respective outfalls at 
flood tide, and before selecting the location careful study should be 
made of this question by means of floats and by examinations of the 
water at various seasons of the year. Again, it will often be found that 
the quality of the water is quite different along the two banks of a 
stream, owing to near-by sources of pollution and to the entrance of 
tributary waters. The location of the intake must also be determined 
with special reference to the lowest water-stage. 

As regards the structural features, the points to be considered are: 
permanency of river-channel, nature of river-bed and velocity of cur¬ 
rent, suitability of adjacent ground for pumping-station and other 
works, and expense of conduit construction from intake to pumps and 
from pumps to distributing system. In the case of a stream of rapid 
fall the question of the head gained by going farther up-stream would 
be an important one. 

286. Intakes in Large Streams Varying Little in Stage.— These are 
of the simplest character. The water may usually be taken from near 
the shore, the end of the intake-pipe being supported on a small foun¬ 
dation of concrete, or on a wooden crib, or by a masonry retaining- 
wall in the case of large works. In the last case some dredging may 
be required in front of the intake, and also wing walls built to retain 
the sloping bank. Gate- and screen-chambers may also be made a 
part of this structure, as in the intake at Philadelphia described below. 

The intake-pipes, usually of cast iron, may lead directly to the 
pumps, thus acting as suction-pipes, or to a gate-chamber and wet-well. 
In the latter case the suction-pipes of the pumps lead from this wet- 
well. Gratings of cast iron or wood, with large openings, are usually 
placed at the entrance to the intake to prevent the admission of large 
objects, while fish-screens of copper of relatively fine mesh are inserted 
in the gate-house or placed over the ends of the suction-pipes. 

Examples. The Queen Lane intake of the Philadelphia water-works 
is illustrated in Fig. 39 .* The intake here is divided into two equal parts, 
each half having three sluiceways 2.96 feet by 4 feet, provided with vertical 


* Proc. Eng. Club Philadelphia, 1897, xm. p. 245. 





RIVER INTAKES. 


251 


sliding-gates at the outer end. Iron screens are placed in front of the gates 
and held in place by masonry walls built out several feet from the face of the 
main wall. Two 48 -inch cast-iron suction-mains lead from each division of 
the intake to the pumps, one for each of the four 20 -million-gallon engines. 
It is to be noted that these suction-pipes are laid somewhat above water-level 
and therefore any leak would allow the entrance of air. Considerable trouble 
was in fact experienced from this cause, and it was not entirely overcome by 
recalking the joints and coating them with asphalt. The intake was con¬ 
structed inside of a V-shaped coffer-dam. A channel 45 feet long extending 
to deep water was excavated in front of the intake. 



Section A B 

Fig. 3 g t —Q ueen Lane Intake, Philadelphia. 


// W 



Fig. 40.—Intake at Hamburg, Germany. 


In Fig. 40 is shown the intake of the Hamburg, Germany, Water-works. 
This is arso a case in which there is little variation in river stage, and the 
arrangement adopted is simple and substantial. 


* M«~ rer. 


Dis Wasserwerk der freien und Hansestadt Hamburg', p. 14* 

































































































































































































252 


RIVER AND LAKE INTAKES. 


288. Intakes in Streams of Ordinary or Great Variation in Water- 
level. —In this case it usually becomes necessary to extend the intake- 
pipe a considerable distance from the banks of the stream in order to 
reach a suitable location at low water. Then in order to enable the 
pumps to reach the water at the lowest stage, which requires them to 
be not more than 1 5 or 20 feet above that level, it is often necessary 
to place them in a deep pump-pit much below high-water level. The 
construction of a water-tight pit for this purpose is then an important 
feature of the works. A method of avoiding this expensive feature for 
temporary works consists in mounting the pumps upon a car which 
may be moved up or down an inclined track built on the river-bank. 
This plan was in use for several years in the old St. Louis works. 

The outer end of the intake-pipe is usually protected by a simple 
timber crib supporting the end of the pipe 2 or 3 feet above the river- 
bottom, and held in place and protected from scour by broken stone. 
A coarse screen or grating is ordinarily placed over that compartment 
of the crib containing the intake-pipe. It is desirable to have the total 
area of the openings of this grating 2 or 3 times that of the pipe itself 
in order to keep the entrance velocity low. Sometimes in order to 
strain out the sediment the crib is entirely filled with broken stone and 
sand to form a filter-crib as illustrated in Chapter XIV. 

Another form of construction at the end of the intake is a masonry 
tower extending above high water and containing ports and sluice¬ 
gates similar in form to those used in reservoirs (Chapter XVI). To 
provide stability against ice and drift the tower is built similar to a 
bridge pier in form, the inlet ports being placed along the sides. The 
arrangement of interior compartments and gates is well illustrated by the 
St. Louis intake described in Art. 289. Heavy cast-iron gratings are 
bolted to the walls just outside the ports. The size of ports should be 
sufficient to keep the entrance velocity down to 2 or 3 feet per second. 

The tower has the advantage over the crib construction in perma¬ 
nence and reliability. It also enables the water to be drawn from 
different levels, and by means of shut-off valves the intake-conduit can 
be emptied at any time and cleaned. For these reasons this form of 
construction is to be commended, but it is much more expensive than 
the crib construction and is therefore suited only for the larger and 
more important works. 

From the crib or inlet-tower the intake-pipe usually runs to a wet- 
well, the end of the pipe being placed at least far enough below low- 
water level to give the head necessary for overcoming the pipe friction. 
It is also desirable that the pipe should be placed at all points below 


RIVER INTAKES. 


25 3 


the hydraulic grade-line, as otherwise it will act as a siphon and require 
special apparatus for removing the air at intervals. From the wet-well 
the suction-pipes lead to the pumps. Provision for flushing the intake- 
pipe may be made by connecting it through a by-pass with the force- 
main of the distributing system. 

Instead of a pipe, a tunnel may be used to conduct the water from 
tower to pumps, short vertical shafts connecting therewith at either end. 
This form of construction will be economical only in the largest works, 
but it is of the most permanent character. 

289. Examples .—A typical arrangement for works situated along a stream 
of wide variation is that at Steubenville, Ohio, illustrated in Fig. 41 .* The 
intake consists of two 24 -inch cast-iron pipes running from a submerged crib 
in the Ohio River to a wet-well 15 feet in diameter and 30 feet deep. This 
well has a shell and top of ^-inch boiler-steel, a Portland-cement bottom, and 
brick lining. From here two 16 -inch suction-pipes extend through a tunnel 
to the pump-pit, the suction never being greater than 15 feet. Provision is 
also made for a third suction-pipe 20 inches in diameter. The pump-pit is 
far below high-water level and is thoroughly water-tight, as is the tunnel and 
well. It has a double wall with a filling of Portland-cement mortar, 1 to 1 . 
The valves in the wet-well may be operated either from above or from the 
tunnel. Messrs. Wilkins and Davison, Pittsburgh, Pa., were the engineers. 



Fig. 41.—Intake at Steubenville, Ohio. 


The general arrangement of intake, and details of the inlet-tower, of the 
St. Louis Water-works are illustrated in Fig. 42 . The intake here is located 
near the northern city limits far above all local pollution and 1500 feet from 
the shore. The exterior masonry of the tower is of granite. The portion 
subjected to the action of the floating ice is rough-pointed, and the remainder 
is quarry-faced. The interior is faced with limestone. Four inlets lead into 
the north chamber, and two into the chamber directly over the intake-shaft, 
but the latter are not ordinarily used. The gates are operated by hydraulic 
cylinders. The screen-chamber is placed on shore adjacent to the wet-well, 
two sets of screens being used of ^-inch and ^--inch mesh respectively. 
Unusual difficulties were encountered in sinking the crib for the inlet-tower 
on account of the rocky bottom and the very swift current of 6 to 8 miles per 
hour. In Fig. 43 are shown details of the gates of the inlet-tower.f These 
are again referred to in Chapter X\ I. 

* Eng. Record. 1898, xxxvm, p. 360. 

f Eng. News, 1891, xxvi. p. 4. Eng. Record, 1892, xxv. p. 319. 




































254 


RIVER AND LAKE INTAKES. 


The new Cincinnati intake furnishes an instructive example of a modern 
and substantial engineering work. It is shown in Fig. 44 . The 
on account of the shape of the river-bed, is located close to the Kentucky 



Inlet Tower 



Wef- We// 




Profile of Tunnel 
Fig. 42.—Intake at St. Louis. 


shore. It is quite similar in general design to that at St. Louis. The tunnel 
is lined with two rings of brick with concrete backing; it is designed for a 
self-cleansing velocity of 3 feet per second. A peculiar feature is the very 
deep pump-pit, made necessary by the great variations in river stage (about 70 
































































































































































































RIVER INTAKES. 


2 si 



Fig. 43. —Gate Details, St. Louis Inlet-tower. 



horizontal Scale. 


Vertical Scale. 


ff.W. LinerEJ.73M 


Natural But ! 


LW.Lim EIA.B O. 


Water-Works. 


Sand 

brave! 

Lime Stone La/ers 


Sand and 
Orave! oj 


5 Limestone 
I42/.00 - 


Stratified 


mne! Oradient about O'25 in IOOJ 


F\g. 44.—The Cincinnati Water works Intake. 

(From Engineering News, vol. xl.) 










































































































































RIVER AND LAKE INTAKES. 



feet). The upper portion of the uptake-shaft is lined with f-inch steel plates, 
and this lining is carried up through the pump-pit as a steel pipe io feet in 
diameter. The suction-pipes of the pumps connect with this shaft near the 
floor of the pump-pit. The masonry walls are 4 feet thick at the top and 
14.5 at the bottom, and to insure imperviousness a ■J-inch steel shell is built 
into the wall. 

290. Intake-works for Gravity Supplies. —Where a stream has a 
rapid fall it may be practicable to conduct the water entirely by gravity 
through a canal or conduit to the place of consumption, or perhaps to 
filters or to pumping-stations. If the stream is small, it will usually be 
desirable to construct a low dam or diversion-weir impounding a small 
volume of water, from which reservoir the conduit may lead. A gate¬ 
house with screens and controlling gates or valves is placed at the 
entrance of the conduit. If coarse sediment is carried by the stream, 
small settling-basins should be provided near the head of the conduit, 
or the reservoir built large enough to act as such. (For descriptions 
of many works of this character see various works on irrigation.) 
Where the stream has a sandy or gravelly bottom it may be practicable 
to construct filter-galleries underneath and yet be able to convey the 
water entirely by gravity. 

In Fig. 45 is illustrated the small diversion-weir of the Simla, 
India, Water-works. The stream is very small, and the weir is so- 
arranged that only the dry-weather flow is caught, the muddy water 
of the floods, which flows at a relatively high velocity, leaping the 
opening and passing on. A somewhat similar arrangement is used at 
Altona, Pa. There the flood-water is conveyed in an artificial channel, 
in the bottom of which is a masonry gutter covered by a grating and 
connected to a pipe leading to the reservoir. The gutter and pipe are 
designed for a maximum capacity of 50 million gallons per day, and 
any flow in excess of this must pass on down the channel. Less can 
be admitted by partly closing a valve.* 

LAKE INTAKES. 

291. Location. —The location of a lake intake in such a position as 
to obtain at all times water of the best quality, and to fulfill the require¬ 
ments of safety against interruption, is a question requiring very careful 
study. In a lake unpolluted by sewage some of the things to be 
investigated are: the location of the mouths of streams and the sedi¬ 
ment carried by them; the character of the lake bottom; the direction 
of wind and currents and their effects in stirring up the mud on the 


* Jour. A T ew Eng. IV. W. Assn., 1899, xiv. p. 151. 





LAKE INTAKES. 


257 


lake bottom and in conveying sediment from point to point; and 
matters pertaining to the quality of the water, such as temperature, 
color, effect of stagnation, etc., as discussed in Chapter IX. (An 
investigation of this character carried out for the city of Syracuse on 


r op css ed ctons 


11 MG CON CRETE, 

C&riEHT 



PWCMIBO 


SECTION 




Skaneateles Lake, a body of very pure water, involved the taking of 
over 3000 soundings.) 

The intake should if practicable be located at a sufficient depth to 
be free from any considerable wave-action, both to secure greater 
stability and to avoid the effect of the disturbance of the sediment by 
the waves. It was shown in Chapter IX that even in small ponds the 
wind stirs up the water to a depth of 15 or 20 feet, so that this may be 
taken as about the minimum depth. A greater depth is desirable if 
bad effects of stagnation are not present, since the water becomes 
rapidly cooler below this point. In large lakes the wave-action 
extends to much greater depths and the intake should be extended 
accordingly to depths of 40 or 50 feet. In such large bodies of water, 




























258 


RIVER AND LAKE INTAKES. 




bad odors from stagnation are little to be feared. Where the water is 
shallow for a long distance from shore, as along Lake Michigan, and 
especially Lake Erie, the best length of intake-conduit becomes too 
great to be afforded by any but the largest cities. 

Most of the cities along the Great Lakes dispose of their sewage by 
running it directly into the lake at the most convenient point; and for 
those places that draw their water-supply from the same body of water 
the most difficult part of the intake problem is to exclude their own 
sewage. As the cities grow, the intakes are pushed farther and farther 
out, but usually not until the necessity of the step is brought home by 
increased mortality from typhoid fever; and, however carefully this 
matter is followed up, the quality of the water taken from such sources 
must always be looked upon with suspicion. In Chicago the length of 
intake has gradually increased to 4 miles. In Milwaukee it is ij- miles, 
while the new intake at Cleveland is about 5 miles long. 

292. The Intake-conduit. —Whether the conduit should be a pipe¬ 
line or a tunnel depends upon the cost of construction and the relative 
reliability of the two forms. In small works the cost of a tunnel would 
be prohibitory, while in the case of a very large intake a tunnel may 
be the cheaper. Again, a pipe-pine, unless sunk very deep, is subject 
to disturbances near the shore end by ice action, wreckage, and scour 
from storms. The best solution may consist of a combination of the 
two, as at Milwaukee, where a pipe is used at the outer end and a 
tunnel at the shore end. 

The size of the conduit will be largely controlled by the permissible 
loss of head from intake to pumps, and this in turn will depend upon 
the available depth of suction and upon the economy of construction 
of conduit, wet-well, and pump-pit. In very long intakes this will 
necessitate low velocities and large sizes. 

The methods employed in executing tunnel work are similar to 
those in other cases where water is to be feared. Excavation is 
usually carried on from the intake-shaft, and often from one or more 
intermediate shafts sunk by the use of large wooden cribs having 
interior wells. Soft strata are penetrated by cast-iron or steel linings, 
with or without the use of compressed air as the case may require. 

Submerged-pipe intakes are usually laid by the aid of divers, 
although other methods have been used. The pipe is preferably laid 
in a dredged trench, at least as far out as wave-action is to be feared, 
and should be covered generally to a depth of 3 or 4 feet. Near the 
shore end the covering should be considerably deeper than this. In 
some instances the pipe has not been covered, but held in place by 


LAKE INTAKES. 


259 


piling or by special anchor-cribs. Various methods of laying sub¬ 
merged pipe are described in Chapter XXIV. Pipes have sometimes 
lifted on account of being emptied of water, but this is unusual and 
cannot happen if the shore end rises above the submerged portion by 
an amount equal to the diameter of the pipe. 

Both cast-iron and riveted steel pipe have been used for intakes. 
Their relative advantages depend upon durability, convenience in 
handling, and cost. Steel is lighter and easier to handle, but at the 
same time more easily disturbed when laid. 

293. Protection-works.—The greater number of lake intakes are 
protected by submerged cribs, but a few of the largest, notably those 
at Chicago and the new intake at Cleveland, have large exposed cribs. 
All these protect shafts at the ends of tunnels. Such cribs are much 
more expensive than submerged ones and require constant attendance 
after completion, but in the case of tunnel intakes an exposed crib is 
necessary in the construction of the end shaft, and to make it perma¬ 
nent is of great advantage in case of future extensions. It also enables 
water to be drawn at different levels. On the whole, however, the 
economy of this form may be doubted; and in the case of the Cleveland 
intake a submerged crib was recommended by a commission of 
engineers, consisting of Messrs. Rudolph Hering, G. H. Benzenberg, 
and Desmond FitzGerald, chiefly on the grounds of expense and of 
trouble with ice. Comparing a submerged crib with an exposed one 
they say:* “A submerged crib, on the other hand, say 10 feet in 
height, in 53 feet of water allows the free passage of ice on the surface, 
and uninterrupted access for the water. In a lake the size of Lake 
Erie stagnation effects would hardly occur in such a position, and the 
water will always be of excellent quality near the bottom. We, there¬ 
fore, recommend a submerged crib for the intake.” Also: “It is 
important that the velocity of the water, where it enters the crib, should 
be reduced to but 3 or 4 inches per second, and that the area of ingress 
be sufficient to produce this result. The evident consequence will be 
that less floating matter will be drawn into the crib.” In a report on 
riiis subject to the city of Buffalo, Mr. E. B. Guthrie recommends the 
submerged crib on practically the same grounds. 

To avoid the entrance of the coarser sediment the open end of the 
intake or the lower port-holes of a closed crib should be 6 or 8 feet 
above the bottom of the lake. 

294. Obstruction of Intakes by Anchor-ice.—The greatest difficulty 


* Abstract of report in Eng. Nexus, 1896, xxxv. p. 117. 




26 o 


RIVER AND LAKE INTAKES. 


. met with in operating lake intakes is due to the clogging of the ports 
by anchor-ice. This consists of needles and thin scales of ice which 
form in moving water and which are of such small size that they are 
readily carried below the surface by comparatively weak currents. 
They cease to form after the body of water has become frozen over. 
On coming in contact with submerged objects these particles of ice 
adhere and soon form large masses difficult to dislodge. Anchor-ice 
has given much trouble at lake intakes both at the exposed cribs and at 
the shallower submerged ones. It is removed in various ways. Com¬ 
pressed air discharged near the port has been effective in some 
submerged intakes. Steam, water from hose, chains drawn back and 
forth through the ports, and pike-poles, are some of the other means 
used. 

As tending to obviate the difficulty with anchor-ice, large port area 
and deep ports should be used; and in the later cribs this feature has 
been observed, the ratio of area of ports to tunnel being about four in 
the later Chicago cribs and eight in the new Cleveland crib. This is 
of equal or greater importance in submerged cribs. In this connection 
note the recommendation of a velocity of 3 or 4 inches per second 
mentioned in the preceding article. 

Anchor-ice is often formed in Northern rivers at points of high 
velocity, but trouble with river intakes may usually be obviated by 



Fig. 46. —Submerged Crib, Milwaukee Intake. 

(From Engineering News, vol. xxxiv.) 


locating the intake at a point where the surface will readily freeze over. 
If this cannot be done, then measures similar to those employed on the 
lakes must be adopted. A method which has been used to advantage 
in dealing with anchor-ice, and one which is applicable to intakes near 
the shore of streams, small lakes, or reservoirs, is to create a quiet body 
of water for some distance around the inlet by means of a raft or boom 
of logs. 














































LAKE INTAKES. 


26l 

295. Examples of Lake Intakes .—It has already been mentioned that the 
Milwaukee intake consists partly of tunnel and partly of cast-iron pipe. 
At the junction of these portions is placed an exposed wooden crib with 
concrete filling, which is provided with emergency inlets. At the outer 
end of the pipe-line is a submerged crib; this is illustrated in Fig. 46. The 
compartment into which the pipe opens is covered with a wooden grating of 
2 X 12-inch planks with 2-inch spaces between, giving 200 square feet of 
opening, or about ten times the pipe cross-section. 

Fig. 47 illustrates the new 2^-mile crib of the Chicago Water-works. It 
is circular in plan and has a central well 60 feet in diameter with a timber 
floor 6 feet thick. The bottom 20 feet is of hemlock timber, and above this 
is a steel shell filled with concrete. After the crib was sunk in place, holes 



Fig. 47.—New 2^-mile Intake-crib, Chicago. 

(From Engineering News , voi. xlii.) 


were cut through the timber bottom and two cast-iron shafts 12 feet in 
diameter were sunk to a depth of 61 feet, below which the lining of the shaft 
is of brick. Water is admitted to the interior well through eight ports 6x6 
feet, located 6 feet above the lake bottom or about 30 feet below the water- 
surface, and at that depth it is thought that trouble from anchor-ice will be 
avoided. From the well the water passes into each shaft through three gates 
41 x 6 feet. The shafts connect with io-foot tunnels. The superstructure 
of the crib includes quarters for the attendants, light-house, boiler- and 
engine-rooms, etc. The total cost was about $200,000.* 


- Eng. News , 1899, xlii. p. 139. 







































































































































































































262 


RIVER AND LAKE INTAKES. 


LITERATURE. 

1. Pearsons. The Water-works of Kansas City. Eng. News, 1887, xviii* 

P- 345 * 

2. The Suction and Siphon Pipe of the Auburn, N. Y., Water-works. 

Eng. News, 1890, xxiv. p. 387. 

3. Feind. The New Water-works of the City of Chicago. Eng. News , 

1890, xxiv. p. 2. 

4. The Geneva, N. Y., Water-works. Eng. Record, 1891, xxm. p. 244. 

5. The New Inlet-tunnel and Tower of the St. Louis Water-works. Eng. 

News, 1891, xxvi. p. 4; Eng. Record, 1892, xxv. p. 319. 

6. Menominee Water-works Iron Intake. Eng. Record, 1892, xxvi. p. 280. 

7. Feind. Chicago New Four-mile Lake Tunnel and its Appendages. 

Eng. News, 1892, xxvm. p. 236. 

8. Water-works Intakes on Lake Michigan. Eng. News, 1893, xxix. 

P- 555 * 

9. The Falcon Rotary Strainer for Water-works Inlets. E?ig. News, 1893, 

xxix. p. 309. 

10. Submerged Water-works Intake at Burlington, Vt. Eng. News, 1894, 

xxxi. p. 512. 

11. Cast-iron Intake-crib for the Water-works of South Milwaukee, Wis. 

Eng. News, 1894, xxxn. p. 70. 

12. Ericson. The Hyde Park or 68th St. Tunnel Extension, Chicago Water¬ 

works. Eng. News, 1894, xxxi. p. 452. 

13. Inlet-crib and Well, Dunkirk Water-works. Eng. Record, 1894, xxx. 

p. 424. 

14. The Nashville, Tenn., Water-works. Eng. Record, 1894, xxx. p. 305. 

15. Hill. The Water-works of Syracuse, N. Y. Trans. Am. Soc. C. E.^ 

1895, xxxiv. p. 23. 

16. The Washburn Park Water-works, Minneapolis, Minn. Eng. Record , 

1895, xxxii. p. 259. 

17. The Milwaukee Water-works New Intake. Eng. Record, 1895, xxxii. 

p. 112; Eng. News, 1895, xxxiv. p. 187. 

18. A Discussion on Anchor-ice. Eng. Record, 1895, xxxi. p. 206. From 

Trans. Am. Soc. C. E., 1894, xxxii. p. 278. 

19. Brough. Submerged Cast-iron Pipe Intake for the Water-works of Erie, 

Pa. Eng. News, 1895, xxxiv. p. 373. 

20. Anchor-ice Troubles at Ottawa, Canada. Eng. Record , 1895, xxxi. 

P- 134 . 

21. Studies for a Water-works Intake at Buffalo, N. Y. Eng. News, 1805, 

xxxiii. p. 309. 

22. The New Rochester Water-works. Eng. Record, 1895, xxxi. p. 346;. 

Eng. News, 1895, xxxm. p. 234. 

23. Smith. Omaha, Neb., City Water-works. Eng. Record, 1896, xxxiv. 

P- 483. 

24. Coggeshall. Anchor-ice. Jour. New Eng. W. W. Assn., 1896, x. 

p. 265. 

25. Ward. Prevention of Trouble with Anchor-ice. Eng. Record, 1896, 

xxxm. p. 314. 


LI TER A TURK. 


263 


26. Hering, Benzenberg, and FitzGerald. Report on Improved Water-supply 

and Sewerage Systems for Cleveland. Abstract, Eng. R'ews, 1896, 
xxxv. p. 117. 

27. The Chicago Water-works Tunnel Extension. Eng. Record, 1896, 

xxxiv. p. 257. 

28. The Newton, N. J., Water-works. Eng. Record, 1896, xxxm. p. 187. 

29. Schulz. The New Lake Tunnel and Cribs for the Cleveland, 0 ., Water¬ 

works. Eng. Record, 1897, xxxv. p. 535. 

30. The New Water-works Intake Tunnel for Cleveland, O. Eng. News, 

1898, xl. p. 82. 

31. Progress on the New Water-works for Cincinnati, O. Eng. News, 1898, 

xl. p. 354; Eng. Record, 1898, xxxvm. p. 513. 

32. Patton. The Municipal Water-works of the City of Duluth, Minn. 

Eng. News, 1898, xxxix. p. 282. 

33. The Grafton, W. Va., Water-works. Eng. Record, 1898, xxxvm. 

P- 539 - 

34. Barrally. The North Tonawanda, N. Y., Water-works. Eng. Record, 

1898, xxxvm. p. 515. 

35. The Steubenville, 0 ., Water-works. Eng. Record, 1898, xxxvm. p. 360. 

36. The Chicago Water-works Extension Tunnels. Eng. Record, 1898, 

xxxvii. p. 538. 

37. New Tunnels, Intake-crib, and Pumping-stations, Chicago, Ill. Eng. 

News, 1899, xlii. p. 139. 

38. Flood-water Channel, Altona Reservoir. Eng Record, 1899, xl. p. 386. 

39. The Water-supply Tunnels of Chicago. Eng. News, 1900, xliv. p. 259, 

el seq. 


CHAPTER XIV. . 


WORKS FOR THE COLLECTION OF GROUND-WATER. 

296. Classification.—The various forms of works built for the collec¬ 
tion of ground-waters may be divided into the following classes: 

(1) Works for utilizing the flow of springs; 

(2) Shallow wells, including ordinary dug wells and tubular wells j 

(3) Deep and artesian wells. 

(4) Horizontal galleries and wells; 

WORKS FOR UTILIZING THE FLOW FROM SPRINGS. 

297. Objects to be Attained.—The chief objects to be accomplished 
in the construction of works of the kind here considered are, the pro¬ 
tection of the water from pollution and the spring from injury through 
clogging or otherwise, the furnishing of a convenient chamber from 
which the conduit-pipes may lead, and, in some cases, the enlargement 
of the yield by suitable forms of construction. Besides these, other 
minor objects are sometimes provided for, according to the necessities 
of the case, such as gate-chambers, settling-basins, measuring-weirs, 
etc. 

298. Ordinary Forms of Collecting-basins.—If a supply sufficient at 
all times for the demand can be obtained from one or more large 
springs, each one should have its separate basin from which the water 
may be conducted to a common main. The simplest form of works 
consists of a small masonry well or basin surrounding the spring and 
from which the conduit-pipe leads. To prevent a growth of vegetable 
organisms and consequent deterioration of the water, such basin 
should always be covered so as to exclude the light. For a small 
spring, a circular well covered with a stone cap cemented in place and 
provided with a manhole is a simple and effective arrangement. For 
larger springs a masonry vault covered with 2 or 3 feet of earth is 
preferable. If the spring is located on a steep hillside, the collecting- 


COLLECTING-BASINS FOR SPRINGS . 


263 


chamber is conveniently constructed in the form of a horizontal gallery 
built into the hill, access to which is had through a door or manhole. 

Overflow-pipes leading into drains or open channels should be pro¬ 
vided for, and to facilitate cleaning and repairs a waste-pipe with valve 
may also be put in, through which the basin can be emptied. Gates 
or valves should also be provided in the conduit-pipe. Weir-chambers 
with suitable floats are an inexpensive but valuable feature, as they 
enable complete records of the yield to be easily obtained. If the 
water carries fine sand in suspension, the basin should be made large 
enough to permit this to settle. 

Mineral and other springs occurring in public places usually have 
open basins, and opportunities are offered in the walls and parapets for 
ornamentation. 

Examples .—In Fig. 48 is shown a simple covered basin. It is 
a type of those used in protecting the Vanne supply of Paris. The 


1 



F IG . 48. —Collecting-basin, Vanne Supply, Paris. 

ground here is quite level. Fig. 49 shows a collecting-chamber on a 
side hill for the water-supply of the city of Lahr. It contains weir, 
settling-chamber, conduit-pipe with strainer, overflow- and waste- 
pipes.* 

* Lueger. Die Wasserversorgung der Stadte, p. 397. 


I 

































266 WORKS FOR THE COLLECTION OF GROUND-WATER. 


299. Methods of Increasing the Flow.—If the natural yield of a 
spring is insufficient, it will sometimes be possible to increase it. The 
proper form of collecting works to accomplish this depends upon the 
character of the spring. It will be here convenient to treat the springs 
under the same classification as in Chapter VII. 

300. Springs of the First Class .—In this class the water appears 
at the upper surface of a stratum of impervious material overlaid by the 
water-bearing deposit, frequently in the form of several small springs. 
Instead of dealing with each one individually it will often be better to 





In Iaf\e CLomler 


6.00 m 




Sectional Plan 

Fig. 49. —Collecting-basin, City ok Lahr. (Lueger.) 


construct a long collecting-gallery running parallel to the outcrop and 
leading to a central collecting-chamber which can be made similar in 
form to that for a large spring. This gallery, which is made similar 
to those described in Art. 356, should be built deep enough to rest upon 
the impervious material, and thus to collect all the underground 
flowage as well as that appearing as springs. The total yield may be 
thus much increased, the increase being relatively greatest during dry 
weather. 

In the case of a single large spring the flow can sometimes be 
increased by opening up the water-passages for some distance into the 























































































THE HYDRAULICS OF WELLS. 


267 


hill, thus decreasing the resistance to flow and possibly drawing from 
a larger area. Such a procedure is likely at the same time to make 
the flow more irregular by drawing more rapidly on the storage 
capacity of the ground, and this plan should hence not be adopted 
without careful consideration. 

301. Springs of the Second Class, or those where an impervious 
layer covers to a greater or less extent the water-bearing stratum.— 
Such a spring may represent but a part of the ground-water flow, and if 
borings indicate a ground-water stream of considerable extent, the col¬ 
lecting-works may be arranged without much reference to the spring. 
Such works will ordinarily be some form of well or gallery like those 
described in subsequent articles. 

In the case of one of the springs described in Art. 92, page 96, a 
well was sunk near by, and after sealing the spring the water rose in 
the well 3 feet higher than before, and 5 feet above the surface of the 
adjacent ground. Extended tests indicated considerably increased 
yield over that of the spring. A similar spring indicated by tests, after 
the construction of collecting-works, an average yield of about 440,00a' 
gallons per day, as compared to an average previous flow of 275,000- 
gallons. In this case the “well is circular, 22 feet in average 
diameter, 24 feet deep, built of open-jointed rubble masonry with a 
lining of brick laid in cement mortar for the upper 18 feet, and is sur¬ 
mounted by a conical shingle roof. It was built at the largest and 
highest of the three springs, and the sites of the other two were sealed 
over by beds of concrete, while the water was kept down by pumping 
from the well. The outlet is 1.5 feet below the top of the well, which 
overflows between times of pumping. ’ ’ * 

302. The Third Class of Springs , which are mere overflows of 
ground water in a porous formation, are to be treated like those of the- 
second class. The ground-water streams of which they are the indi¬ 
cations may frequently be drawn upon to advantage by wells or 
galleries arranged with little reference to the springs themselves. 

THE HYDRAULICS OF WELLS. 

303. Before entering upon a discussion of the various forms of wells- 
it will be desirable to consider the hydraulic principles governing the 
flow of water into them from the surrounding porous formations. 
There are two general cases to be considered: (1) Flow into ordinary 
wells, where the upper surface of the ground-water is exposed to at- 


* four. New Eng . W. W. Assn., 1896, XI. p. 156. 




268 


WORKS FOR THE COLLECTION OF GROUND-WATER. 


mospheric pressure through the porous ground above. (2) Flow into 
artesian wells, where an impervious layer covers the porous one, thus 
enabling the water to flow under a pressure greater or less than the 
atmosphere. General formulas relating to these two cases will be dis¬ 
cussed separately, after which matters common to both will be 
considered. 

A. Principles Governing the Flozv into Ordinary Wells. 

304. General Form of Ground-water Surface.— If a well, sunk into a 
body of ground-water, be drawn from, the level of the water in the 
well will be lowered, and the surface of the ground-water adjacent to 
the well will assume a form similar to that shown in Fig. 50. In this, 



Fig. 50. —Section through Well. 


AB is the original surface and CDEF the new surface. The amount 
which the surface is lowered decreases rapidly as we get farther from 
the well, until at some point more or less remote there is no sensible 
effect. The area within which the level is appreciably lowered is called 

the circle of influence. 

If the ground-water is present merely as a pond or reservoir and 
the pumpage exceeds the percolation on the area, the circle of influence 
will gradually enlarge until it includes the entire area of the pond, and 
the water will in time be exhausted. If there is, however, a general 
flow of the ground-water, a well will be lowered only until the circle 
of influence has broadened out far enough to cause to be tributary to 
the well an area into which the flow of water is equal to the pumpage. 

305. Derivation of Formula for Flow.—In Fig. 50 let it be assumed 
that AB, the original surface of the ground-water, is horizontal and at 
a uniform distance H above an impervious stratum; that the porous 
material is uniform; and that the well is sunk to the impervious stratum. 

















THE HYDRAULICS OF WELLS. 


269 


Let r = radius of well, h — depth of water in the well when in opera¬ 
tion, H — original depth of ground-water, x and y — co-ordinates of 
any point of the curve CF referred to the bottom of the well as origin, 
and Q = rate of flow into the well, or the yield. 

The total available head, as represented by H — h , is consumed in 
four ways: first, and mainly, by the resistance to flow in the ground; 
second, by the entrance resistance into the well-tube or well; third, 
by friction in the well-tube in ascending to DE\ and fourth, by the 
head necessary to give the rising water its velocity. For shallow wells 
all but the first are usually very small, and for the present they will be 
neglected. Their effects in exceptional cases are noted farther on. 

The equation of the curve CD-EF will now be derived. The flow 
being radial, the area of the cross-section through which the water 
passes at the rate Q at any distance x from the center is that of a 
cylindrical surface equal to 2 nxy. In Chapter VII, Arts. 85 and 88, 
it was shown that Q in cubic feet per day = ksAp , where k = a con¬ 
stant depending on fineness of sand, = 8200 X (effective size of sand) 2 , 
^ = slope, A = area of cross-section in square feet, and p = porosity. 

dy 

In this case A — 2 nxy and ^ whence 


dy 

Q = 2nk P x y dx 


0 ) 


Writing this in the form Q 


dx 


x 


2 nkpydy, and integrating, we have 


Q log* ;r = nkpy 2 -f- C, . 

in which log, is the natural or hyperbolic logarithm of ;r. 

When x — r, y — h, whence we find C — Q log, r — nkph 2 , 
substituting and solving for y 2 we have 

o 


y 2 — 


x 


log, -- + 
7 i fcp r 


(2) 


and 


(3) 


which is the equation sought. The units are the foot and day. 

This formula assumes the water to flow towards the well from an 
indefinite distance, and the curve therefore continues to rise indefi¬ 
nitely, but more and more slowly as we recede from the well. In the 
actual case the circle of influence is limited on account of the flow of 
the body of ground-water, this flow being maintained by percolation 
either near or remote. Furthermore, on account of the slope of the 
ground-water surface, the curve will be modified, being steeper on the 
up-stream and flatter on the down stream side. It will also be more 
or less irregular on account of variations in the porosity of the ground. 





270 WORKS FOR THE COLLECTION OF GROUND-WATER. 


But the general form of the curve as determined by actual measure- 
ments agrees quite closely with the theoretical curve, and valuable 
general conclusions may be drawn from a theoretical consideration of 
the subject. 

If in equation (3) R be that value of x for which the change 
in water-level is inappreciable, equal to the radius of the circle of 
influence, the corresponding value of y will be H, the original depth of 
water, and we have 

Q V 


H 2 = 


. log* — 4 - /i 2 , 
nkp r ' 


and solving, we get for Q in cubic feet per day 

7 H 2 
Q = nkp — 


or, in gallons per day, 


lo §<7 


0 = 7 - 5 *' 


h 2 H 2 - h 2 
— k 


. R 

1 o S.o - 


m - ip 


log 


R 


( 4 > 


( 5 > 


10 


Tlkl) 

in which k' — -, a constant depending upon the fineness and the 

2.30 

porosity of the material. All distances should be expressed in feet. 

306. Calculation of Flow,—In Table No. 52 are given values of k r 
for various values of porosity and size of sand-grain. Table No. 53 
contains values of Q in gallons per day for various values of R and r y 
and for a constant value of k' equal to 100, and of H 2 — h 2 also equal 

k' 

to 100. To find Q for other values of k’, multiply by —and for 

H 2 - h 2 

other values of H 2 — h 2 multiply by 


100 

TABLE NO. 52 . 

VALUES OF k' IN THE FORMULA Q = 7.5^' 


H* - h> 

lo sqr 


Effective Size of Sand Grains in Millimeters. 


0 0 

0 

a, a. 

.IO 

.20 

• 30 

.40 

•50 

.80 

1.00 

2.00 

3 00 

20 

22.4 

89 

202 

358 

560 

1430 

2240 

8,960 

20,200 

25 

28.0 

112 

252 

448 

700 

1790 

2800 

11,200 

25,200 

30 

33-6 

134 

302 

537 

840 

2150 

3360 

13,400 

30 200 

35 

39 - 2 

157 

353 

627 

980 

2510 

3920 

i5,7oo 

35 , 3 oo 

40 

44.8 

179 

403 

717 

1120 

2860 

4480 

17,900 

40,300 
































THE HYDRAULICS OF WELLS . 


27t 


TABLE NO. 53 . 


YIELD IN GALLONS PER DAY OF SINGLE 

FROM FORMULA 


WELLS FOR k' — IOO AND 
H ' 2 - h 2 


<2 = 7 - 5 ^ 


1 R 
log- 


H' - K> = ioo. 


R . 


Yield in Gallons per Day of Wells having Diameters of 


Feet. 

2 in. 

4 in. 

6 in. 

8 in. 

12 in. 

2 ft. 

4 ft. 

10 ft. 

20 ft. 

40 ft. 

IOO 

24,000 

27,000 

20,000 

30,000 

33,000 

37,000 

44,000 

58,000 

75,000 

110,000 

200 

22,000 

24,000 

26,000 

27,000 

29,000 

32,000 

37.ooo 

47,000 

58,000 

75,000 

500 

20,000 

22,000 

23,000 

24,000 

25,000 

28,000 

31,000 

37,oco 

44,000 

54,000 

1,000 

18,000 

20,000 

21,000 

22,000 

23,000 

25,000 

28,000 

33,000 

37,000 

44,000 

2,000 

17,000 

18,000 

19,000 

20,000 

21,000 

23,000 

25,000 

29,000 

33,ooo 

37,000 

5.000 

16,000 

17,000 

17,000 

l8,OOC* 

19,000 

20,000 

22,000 

25,000 

28,000 

31,000 

10,000 

15.000 

16,000 

16,000 

17,000 

18,000 

19,000 

20,000 

23,000 

25,000 

28,000 


The formula or tables will enable approximate values of Q to be 
determined if all the other quantities are known. With shallow 
deposits no great difficulty arises in estimating rough values for k\ p , 
and H; h is determined by the conditions under which the well is to 
be operated, and r is the known radius of the well. 

307. The Value of R. — In none of the above quantities is there 
anything that involves the amount of water actually flowing in the 
ground, and it is obvious that without some knowledge of this no 
formula will enable one to predict the yield of a well. The effect of 
this element is all included in the value of R , the radius of the circle 
of influence, and it is in the determination of this that the chief difficulty 
arises; but it will be noted from Table No. 53 that large variations in 
R affect Q but little, so that a rough approximation will be sufficient. 
This can be obtained by properly conducted tests as explained in Art. 
316, or it can be estimated as follows: Assuming that all the water in 
the circle of influence flows into the well, the width of the strip of the 
ground-water stream tributary to the well will be 2 R, and the original 
cross-section of this portion of the ground-water stream is 2 RH. Then, 
as on page 269, the quantity Q = ks X 2RH X p, whence 


R = 


Q 


2 ks Up 



By substituting the value of Q from equation (4) we have, after reduc¬ 
tion, 


n(H* - li z ) 

R = 

2 sH log, - 


( 7 ) 

































2,72 WORKS FOR THE COLLECTION OF GROUND-WA TER. 


or, as H — h is usually small compared to H , we have approximately 


R = 


n{H — Ji) 

s log, — 
r 


1.36 


H - h 
s log IO y 



from which, knowing the slope s and the depression of the water-level 
(H — Ji), R can be estimated with sufficient accuracy by a few trials. 

It is to be noted that R varies inversely with the slope, and from 
eq. (5) it is seen that Q increases as R decreases; hence for a given 
value of ( H 2 — Ji), Q will be greater the greater the slope, and with 
zero slope Q will be zero. This is an important point; it expresses 
mathematically what has been stated in Chapter VII, that there must 
be an actual flow of the ground-water a§ shown by an hydraulic slope 
in order that any definite quantity can be withdrawn for an indefinite 
length of time. 

Table No. 54 gives values of R from eq. (8) for various values of r 

H - h 
and of-. 


TABLE NO. 54 . 


VALUES OF R IN FORMULA R — I. 


36 


H - h 

~ R 

sl ° e- 


FOR VARIOUS VALUES OF 


H - h 
s 


AND OF r. 


1 

* 

Diameter of Well (= 2r). 

s 

6 Inches. 

1 Foot. 

2 Feet. 

4 Feet. 

10 Feet. 

20 Feet. 

200 

104 

115 

129 

146 

176 

207 

400 

189 

208 

230 

258 

305 

352 

600 

269 

295 

325 

362 

423 

485 

800 

347 

378 

415 

461 

536 

6lO 

1,000 

422 

459 

503 

556 

645 

730 

2,000 

779 

843 

919 

IOIO 

1150 

1290 

4.000 

1450 

1560 

1690 

1840 

2080 

2300 

6,000 

2080 

2240 

2410 

2620 

2950 

3250 

8,000 

2700 

2890 

3120 

3370 

3780 

4150 

10,000 

3280 

3530 

3800 

4IIO 

4590 

5030 


308. Example .—To apply these tables to an example let it be 
required to estimate the yield of a 6-inch well sunk into a ground-water 
stream 30 feet thick, the water-bearing stratum consisting of a coarse 
sand of an effective size of 0.4 millimeters and a porosity of 20 per 
cent. Further, suppose the slope a = 10 feet per mile = .0019, and 
that the water is to be drawn down 5 feet below its original level. Then 

H - Ji 

H — h — 5, Ji — 25, - = 2600, and H 2 — Ji — 275. From 




























THE HYDRAULICS OF WELLS. 


273 


Table No. 54 we find for - == 2600, R == about 1000 feet. 

From Table No. 52 we find for d — 0.4 and p — 20 per cent, k' = 
358. Finally, in Table No. 53, we find for R = 1000, k' = 100, and 
H 2 — h 2 — 100, a value for Q of about 21,000; whence for k' — 358 
and H 2 — li 2 ^ 275, Q = 21,000 X 3.58 X 2.75 = 207,000 gallons 
per day. 

309, Effect on the Yield of a Change in the Various Elements.—The 

value of Q from eq. (5) is seen to vary directly with k\ a constant 
which varies directly with the square of the diameter of sand-grains and 
with the porosity of the material. Furthermore, Q varies inversely as 

D 

log—, and the values given in the table show how little Q is changed 

by considerable changes in the values of either R or r. Thus, other 
things being equal, a 2-foot well will yield but 15 to 30 per cent more 
than a 3 inch well. 

Eq. (4) may be written in the form 


Q = k 




log 


R 



or if H and h are nearly equal, as is usually the case, we may write 
approximately 


Q 


= 2 k 


,H(H- h) 




from which it is seen that Q is directly proportional to H and also to 
H — hy that is, to the depth of ground-water and to the depression of 
the water-surface. Thus if in pumping at the rate of 100,000 gallons 
per day from a well the water-surface is depressed 2 feet, approximately 
200,000 gallons may be obtained by lowering the surface 4 feet. If 
the lowering is too great, then eq. (10) becomes more in error and Q 
will increase less rapidly than the value of H — ft. This general 
relation that Q varies with H — h has been shown to be very nearly 
correct in many cases by actual tests and is an important principle to 
keep in mind. 

B. Principles Governing the Flow into Artesian Wells. 

310. Where the water flows under pressure in a porous stratum 
overlaid by an impervious one, the flow into a well is not accompanied 
by a change of level in the surface of the water, but the curve of pres- 






274 WORKS FOR THE COLLECTION OF GROUND-WATER . 


sures is of a form similar to the water-surface in the case already- 
treated. 

In Fig. 51 the thickness of the porous stratum is t, the original 


Ground Lere/ 


A. 

<T 


Impervious Stratum 


lb- 


— ~ —-__ _ jr 

— ^Pressure Line 


y 


-t> -T 


er- 


Porous Stratum 


H 


Fig. 51.—Section through Artesian Well. 


pressure-line is AB (below or above the surface), and the pressure-line- 
existing on pumping from the well is CD-EF. The derivation of the 
equation of the curve of pressures is similar to that in Art. 305, except 
that in this case the water passes through an area of constant depth t 
instead of a variable depth y. Making this change, eq. (1) of Art. 
305 becomes 


Q — 2 Ttkpxt 


dy 

~dx' 


(11) 


from which we readily get, as before, 

,,H - h 

Q = .(12) 

io S J 

in which k' — the same constant as before, given in Table No. 52, 
t — thickness of porous stratum, H — original pressure-head at the 
bottom of the stratum, h = head at bottom of well when flowing, R = 
radius of circle of influence, and r = radius of well. 

This equation differs from (5) only in having the constant 2 t in 
place of (H + k), and hence the laws of flow are very nearly the same 
as in the previous case; that is, Q varies directly with k\ also with 
H — h (the lowering of the water in the well), and with /, and in¬ 
versely with log R. 

Where an artesian stratum lies near the surface it can be investi¬ 
gated with respect to hydraulic slope, material, and depth as readily 
as the other class already discussed, and estimates of flow made in the 




















THE HYDRAULICS OF WELLS . 


275 


same way. In using Table No. 53 > 2 t{H — JA should be used in place 
of H 2 - h\ 

In the case of deep artesian wells t is sometimes several hundreds 
of feet, and H — h is also often very large. On the other hand k' is 
usually small, and likewise the slope, but on the whole the values of 
Q will usually be much larger than for shallow wells. 

An important test showing the variations of Q with H — h was 
carried out by Prof. Marston on a well 2215 feet deep at the Iowa 
Agricultural College in which the lowering of the water was very 
great.* The results were: 

Lowering of Water-level. Yield. 

120 feet.10.2 cubic feet per minute 

162 “.“ “ “ 

184 “.15.1 “ “ << << 

238 “. . .18.8 “ “ “ “ 

Using the value of 10.2 as a basis, exact proportion would call for 
yields of 13.8, 15.7, an d 20.3 cubic feet respectively. 

C. Considerations of General Application. 

311. Pipe Friction and Other Losses of Head.—The resistances to 
flow that have not been considered are the friction of entrance into the 
well-tube or well, the friction in the tube itself, and‘the velocity-head. 

Inadequate area of openings into the well, and the effects of 
clogging and corrosion, may cause the loss of head at entrance to be a 
very considerable proportion of the total head. This question is further 
discussed in connection with the constructive features. The velocity- 
head is usually too small to be worth considering. It is easily figured 

in any case from the formula h = —. 

The friction-head in wells up to 50 or 100 feet in depth is usually 
small, but in deep wells of small diameter it is often a very large item 
and needs to be carefully considered. If the well is cased for a large 
portion of its length, the friction can be figured on the basis of the fric¬ 
tion in wrought-iron pipes. Where not cased the friction would prob¬ 
ably be greater, the amount depending on the roughness of the walls. 
It will be sufficiently accurate for present purposes to estimate it as 25 
per cent greater than that for smooth pipes, and Table No. 55 has been 
computed on that basis. It gives the frictional head for wells 100 feet 
deep of various diameters and under various rates of flow. By the use 


* Eng. Record, 1898, xxxvn. p. 387. 







2 j 6 WORKS FOR THE COLLECTION OF GROUND-WATER . 


of this, together with the principle that the loss of head due to the 
resistance in the ground is closely proportional to the flow, we may 
compute the total head required to cause any given yield from a well, 
if we know the yield for any particular head; or, knowing the flow 
from a well, we can compute approximately the yield of wells of other 
sizes sunk to the same formation. 

TABLE NO. 55 . 


LOSSES OF HEAD IN TUBULAR WELLS DUE TO FRICTION IN WELL-TUBE OR WELL. 


cj • 

C • v +* 

O -a a« 

1; v " 



Discharge in Gallons per Day. 



•~e «g 
£ ^ 

2-inch. 

3-inch. 

4-inch. 

6-inch. 

8-inch.. 

10-inch. 

12-inch. 

0.5 

13,000 

39.000 

84,000 

250,000 

550,000 

1,000,000 

1,600,000 

1 

19,000 

56,000 

120,000 

350,000 

830,000 

1,500,000 

2,400,000 

2 

28,000 

84,000 

180,000 

550,000 

1,200,000 

2,200,000 

3,600,000 

3 

35.ooo 

110,000 

230,000 

700,000 

1,500,000 

2,700,000 

4,600,000 

4 

42,000 

120,000 

270,000 

830,000 

1,800,000 

3,200,000 

5,300,000 

5 

47,000 

140,000 

310,000 

940,000 

2,000,000 

3 700,000 

6,200,000 

6 

53,000 

160,000 

350,000 

1,000,000 

2,300,000 

4 200,000 

6,900,000 

8 

62,000 

190,000 

400,000 

1,200,000 

2,600,000 

4.700,000 

7,900,000 

10 

69,000 

210,000 

470,000 

1,400,000 

3,000,000 

5,500,000 

9,000,000 

15 

90,000 

270,000 

590,000 

1,700,000 

3,800,000 

7,000,000 

12,000,000 

20 

100,000 

310,000 

690,000 

2,000,000 

4,600,000 

8.300,000 


30 

130,000 

400,000 

860,000 

2,600,000 

5,600,000 

10,000,000 


40 

150,000 

460,000 

-a 

1,000,000 

3,000,000 

7,000,000 




312. Illustrative Calculations. —1. Suppose a well 6 inches in diameter and 
500 feet deep yields 500,000 gallons per day, with a total head of 15 feet. 
Let it be required to find the head necessary for a discharge of 1,000,000 
gallons daily. In the first case the loss of head by friction is, from the table, 
about 9 feet, and, neglecting other losses, the head consumed in the strata 
is therefore 6 feet. To discharge 1,000,000 gallons requires about 12 feet head 
in the ground and 30 feet in pipe-friction = 42 feet total required head, or 
an added head of 27 feet over that required for a yield of 500,000 gallons. 

2. Suppose a 6-inch well 1000 feet deep yields 1,000,000 gallons per day 
under a total head of 100 feet. What will be the yield of a 4-inch well under 
the same head ? 

From Table No. 55 the frictional head in the 6-inch well is about 60 feet, 
and, neglecting other losses of head, the head lost in ground friction is 
100 — 60 = 40 feet. For other volumes it will be assumed that the head lost 
in ground-friction is proportional to the volume. The problem now is to 
determine an amount Q for the 4-inch well such that the total loss, pipe fric¬ 
tion and ground friction, shall be 100 feet. It is readily solved by trial. 
Thus for various values of Q the losses of head are: 

Q . Pipe Friction. Ground Friction. Total. 

470,000 IOO 19 119 

400,000 80 16 96 

Hence for a total head of 100 feet Q will be about 420,000 gallons per day. 

3. As illustrating the effect of size of well where the pressures and depths 
are great, values of Q have been computed for various sizes of wells in accord- 





















THE HYDRAULICS OF WELLS. 


277 


ance with the data of example 2, so that the total loss of head is about 100 
feet in each case. They are given in the adjoining table together with the 
losses of head. 


Diameter 

Q • 

Pipe Friction. 

Ground Friction. 

of Well. 

Galls, per day. 

Feet. 

Feet 

2-inch. 


97 

3 

3 “ . 


90 

8 

4 . “ . 


85 

16 

6 “ . 


60 

40 

8 “ . 


35 

64 

10 “ . 


18 

84 

12 “ . 


9 

92 


From this it is seen that for wells of small diameter and with high 
pressures the yield is principally dependent upon the pipe friction, but that 
with large diameters the yield depends rather upon the ground friction and is 
little affected by the diameter. 

313. Examples of Wells Flowing under High Heads —In the Dakota 
artesian basin the pressures run up to 300 feet and over, thus giving rise to 
high velocities and large losses of head from pipe friction. The great differ¬ 
ences in yields from different-sized wells there noted are largely due to this 
fact. Below are given data of several typical wells taken from the United 
States Geological Survey Report, 1895-6, Part II. A column of “ computed 
yields ” has been added, the computations having all been made on the basis 
of the flow of the 8-inch wells and on the assumption that all the water flows 
the entire length of the well. Only roughly approximate results could of 
course be expected, as the wells are distributed over a large area and the 
water-bearing stratum is more or less irregular; and, besides, the observed 
yield is doubtless in many cases from very rough measurements. The reported 
yields for some of the smaller wells would be impossible under the given head 
if all the water entered at or near the bottom. 


TABLE NO. 56 . 

DATA OF ARTESIAN WELLS IN THE DAKOTA BASIN. 


Diameter, 

Inches. 

Depth, 

Feet. 

Static 

Head, 

Feet. 

Yield. 

Observed 
Gals, per Min. 

Computed, 
Gals, per Min. 

I 

480 

142 

30 

16 

2 

715 

303 

200 

IOO 

2 + 

880 

262 

280 

180 

3 

689 

300 

425 

320 

3 

1315 

287 

350 

210 

4 i 

840 

345 

IOOO 

900 

4I 

902 

352 

670 

750 

6 

712 

276 

1500 

1700 

6 

897 

142 

1200 

IOOO 

6 

1350 

138 

500 

850 

8 

530 

198 

3292 

2600 

8 

IOOO 

345 

2000 

3200 

8-10 

640 

253 

4350 

4000 


314. Effect of Depth of Well.—It has been assumed in the preceding 
discussion that the well penetrated to the impervious stratum. If it 


























27S WORHS FOR THE COLLECTION OF GROUND- WA TER. 

reaches short of this, there will evidently be increased resistance near 
the well for like quantities of water, or for the same head the flow will 
be decreased. This added resistance due to decreased cross-section 
occurs only in the immediate vicinity of the well, and if the total loss 
of head or total depression is great, and if the well extends half or 
two-thirds through the porous stratum, the added resistance will be 
but a small proportion of the total and the consequent effect on Q will 
not be great. It often happens that the water-bearing formation is 
made up of layers of different degrees of porosity, so that the resistance 
to flow from one stratum to another would be very great. In this case 
the yield would be very largely influenced by the depth of the well. 

315. Mutual Interference of a Number of Wells—If two or more 
wells penetrating to the same stratum are placed near together and 
simultaneously operated, the total yield will be relatively much less 
than the yield of a single well pumped to the same level. This mutual 
interference of wells depends in amount upon the size and spacing of 
the wells, upon the radius of the circle of influence of the wells when 
operated singly, and upon the depth to which the water is lowered by 
pumping. Professor Slichter has investigated this subject theoretically,* 
and some examples given by him of the application of his formulas will 
be instructive. 

Assuming the wells in question to be 6 inches in diameter, that the 
water is lowered 10 feet by pumping, and that R = 600 feet, the 
mutual interference of a group of two wells, a group of three wells, and 
of a large number of wells placed in one row are as given in the fol¬ 
lowing table. The amount of the interference is expressed as the per¬ 
centage of reduction in yield per well below that of a single well 
uninfluenced by others. According to the figures given in the table 

TABLE NO. 57 . 

MUTUAL INTERFERENCE OF GROUPS OF SIX-INCH WELLS. 

(Water lowered 10 feet by pumping. R = 600 feet.) 


Two Wells. 

Three Wells. 

Large Number of Wells in a 
Row. 

Distance Apart 
of Wells. 
Feet. 

Interference. 

Per cent. 

Distance Apart 
of Wells. 
Feet. 

Interference. 

Per cent. 

Distance Apart 
of Wells. 
Feet. 

Interference. 

Per cent. 

5 

38 

5 

55 

IOO 

66 

10 

35 

10 

5 i 

200 

45 

100 

20 

100 

3 i 

400 

24 

200 

16 

200 

22 

600 

14 

400 

11 

400 

12 

IOOO 

6 

1000 

6 

1000 

8 




* Report U. S. Geolog. Survey, 1897-98, p. 371. 

















THE HYDRAULICS OF WELLS. 


279 


two wells 200 feet apart will yield 84 X 2 = 168 per cent as much as 
a single well. If a third well be placed between these two, the yield 
will be 69 X 3 = 207 per cent as much as the single well. If a large 
number of wells are placed 100 feet apart, the yield of each is but 34 
per cent as much as it would be if operated alone. 

316. Determination of Yield by Tests—Where it can be done, the 
best way to determine Q is by actual tests conducted for a sufficient 
length of time to bring about a condition of equilibrium in the flow, 
but unless this condition is approximately fulfilled such tests are apt to 
be very deceptive. With a flat slope to the ground-water a test may 
be carried on for weeks and even months, and the circle of influence 
will still continue to widen, resulting in a gradually decreasing yield. 
It may thus require years of operation to bring the conditions to a final 
state of equilibrium except as affected by variations in the percolation. 
The steeper the slope the quicker the conditions become constant; and 
to aid in judging of results obtained by pumping tests, the ground-water 
slope should be determined when possible. 

In conducting tests on shallow wells it is desirable to observe the 
variations in ground-water level at different distances from the well. 
This will aid in determining when equilibrium has been reached, and 
will also enable R to be estimated and will give information as to the 
proper spacing of a series of wells. 

The value of Q being found for the test well, the effect of variation 
in the size of the well and in the lowering of the water-level can be 
determined from the theoretical considerations already discussed. As 
a valuable check on results of tests, the yield should, where possible, 
be estimated by the method explained in the preceding articles. 

As an example of long-continued lowering, the operation of the 
large well in Prospect Park, Brooklyn, may be cited. The water-level 
varied as follows: 

Volume Pumped Elevation of Water- 


uate * per Day. level above Tide. 

Gallons. Feet. 

1869 . o 14.55 

1870 . 300,000 I4.15 

1871 . 272,000 I3.O3 

1872 . 437,000 IO.56 

1873 . 288,000 II.29 

1874 . 333^000 10.70 

1875 . 294,000 9.83 

1876 . 235,000 9.83 

1877 . 252,000 9.21 

1878. . . .. 249,000 8.80 

1879. ...c . 260,000 8.85 













28o works for the collection of ground-water. 

The actual capacity of the well appears thus to be about 250,000 
gallons per day. 

317, Wells Sunk into Strata in which the Flow takes Place through 
Fissures, —The preceding analysis has been based upon the assumption 
that the water flows through the interstices of the porous material. In 
some rock formations, however, much of the flow undoubtedly takes 
place through fissures. This is apt to be the case with limestone 
strata, the passageways in this material sometimes assuming large 
dimensions, due to the solvent action of the water. 

The effect of these fissures is greatly to increase the capacity of the 
material and at the same time to modify the law of flow. The resist¬ 
ance to flow through large fissures will vary approximately as the 
square of the velocity, instead of as the first power; and as one result 
the yield of a well supplied largely in this way will not increase at the 
same rate as the lowering of the water in the well, but much more 
slowly. As a matter of fact most wells in sandstones do follow 
approximately the law of the proportionality of yield and head, but it 
has been observed in the case of some limestone wdls that there is a 
large departure from it in the direction above indicated. 

CONSTRUCTION OF WELLS. 

318, Forms of Construction, —The various forms and sizes of wells 
used to collect ground-water may be divided into the following classes: 
(1) Large open wells; (2) shallow tubular wells; and (3) deep and 
Artesian wells. 

No sharp line of division can be said to exist between shallow wells 
and deep wells, and in many matters that which applies to one class 
applies equally well to the other. It will, however, be convenient to 
divide them into the above classes, the methods of construction, of 
investigation, and of operation being in many respects different in wells 
of 25 feet to 100 feet deep than in wells of greater depth. One 
hundred feet may be roughly taken as the limit of shallow wells. 

319, Location of Wells. —To procure water economically in the 
large quantities required for public supplies, it was made evident in the 
discussion on the flow of ground-water that there must be present a 
water-bearing formation of considerable extent and porosity. The 
location of such a deposit is here supposed to have been determined 
upon through borings and tests, and as a general requirement the 
works for collection should be so placed as to intercept for a given 
expense as large a quantity of water as possible. 


CONSTRUCTION OF WELLS . 


28l 


It has been shown that the more the water in a well is lowered the 
greater is the yield. A favorable location for a well-plant will therefore 
usually be at a point where the ground-water is reached with the least 
lift of the pumps. This will ordinarily be on low ground and often in 
the vicinity of surface streams. If wells in such a situation are pumped 
too low, they will draw water from the stream as well as from the 
ground-water, a result sometimes undesirable. In some cases it may 
be allowable to obtain filtered surface-water in this way, but this use of 
wells will be discussed subsequently. For the present it will be 
assumed that all the flow is strictly ground-water. 

320. Relative Advantages of Large and Small Wells,—The yield of 
any form of well is a question rather of the flow of the ground-water 
and of the area made tributary by the depression of the water-level in 
a \Vell, than a question of the size or form of construction. The 
discussion in Art. 309 shows that the effect of size alone is very small, 
and that therefore we need not expect an increase in the yield of large 
wells commensurate with increase in size. The increase in flow is. 
however, something; and in the case where the circle of influence is 
small, or where the water is present in large quantities, the increase 
may be very considerable. 

The large well possesses a great advantage over the small well in 
its storage capacity. If the pumping is carried on at a variable rate, it. 
thus acts to increase greatly the real capacity of the large well over 
that of a series of small tube-wells. Furthermore, in the operation of 
the pumps there are many advantages in being able to get the entire 
supply from a single well, or from two or three large wells close 
together, chief among which is the avoidance of long suction-pipes. 
The large well is also of great advantage where it becomes necessary 
to lower the pumps, as it permits the use of a more economical form 
of pumping machinery. 

Trouble is often experienced in the small wells through clogging 
and the entrance of fine sand. This is largely avoided in the large 
well, as the entrance velocity of the water is very small. Opportunity 
is also given for the settling of fine material. 

The chief disadvantage of the large well is in its great cost com¬ 
pared to the tube-well for like yields. This disadvantage increases 
rapidly as the depth increases, and where it may be economy to con¬ 
struct a large well to a certain depth to serve as a pump-pit it will 
usually be cheaper to develop the yield by sinking tube-wells from the 
bottom, or by driving galleries therefrom, than by further sinking. 


282 WORKS FOR THE COLLECTION OF GROUND-WATER . 


Except where used as pump-pits it will seldom be economical to adopt 
the large well for depths exceeding 30 or 40 feet. 

It may be said, therefore, that large wells are suited for places where 
the water can be reached at moderate depths, where the excavation is 
not difficult, where a single large well will furnish the desired amount, 
and where the pumps are to be operated but a few hours of the day. 
The tubular well is particularly suited for developing a supply from a 
wide area and from strata of irregular character, and for penetrating 
deep strata. 

Large Open Wells. 

321. Size and Depth of Wells.—Large wells for water-works are 

constructed of diameters of 10 feet or less to as great as 100 feet, 30 to 

• 

50 feet being the most common size. The best size must be deter¬ 
mined from a consideration of the various factors mentioned in Art. 
320; but as the cost of a well increases with increase in diameter more 
rapidly than does the yield, a very large diameter should be adopted 
only after most careful consideration. 

322. The minimum depth of a well is determined by the depth 
necessary to reach and penetrate for a short distance the water-bearing 
stratum, allowing a margin for dry seasons. Beyond this it should be 
extended to allow for storage, and to permit of such a lowering of the 
water-level as is estimated will be the most economical with the form 
of pump employed, or such as will be necessary to secure the desired 
amount of water. 

323. Construction.—In the first place, it is to be noted that large 
quantities of water will be met with, and if the excavation is to be 
made in the open, adequate means of handling it must be provided. 
As the water-level must be kept at the lowest level of the excavation, 
the maximum pumpage will be considerably more than the future 
capacity of the well. For moderate depths the excavation can be 
carried on with no other aid than sheet-piling. If the well is of large 
diameter, an annular trench is usually first excavated and the curb or 
lining built therein, after which the interior core is removed. This 
method enables the sheet-piling to be readily braced. A method 
adapted to smaller wells is to drive the sheet-piling outside of a series 
of wooden frames or ribs, and to excavate the entire well at once. 
The ribs are built in place as the excavation proceeds. This method 
is illustrated in Fig. 53, page 284. 

For wells of considerable depth sunk in soft material, the curb may 
be started on a shoe of iron or wood, and the excavation and the con- 


LARGE OPEN WELLS. 


283 


struction of the curb carried on simultaneously, the curb sinking from 
its own weight. The material may be either excavated in the ordinary 
way, or by the use of compressed air, or dredged out without attempt¬ 
ing to keep out the water, the method used depending upon depth of 
well, quantity of water, and character of the material. Where the fric¬ 
tion becomes too great to sink the first curb the desired distance, a 
second curb with shoe may be sunk inside the former. In Fig. 52 are 
illustrated two forms of shoes used in sinking wells. These are both 
constructed mainly of wood. To strengthen such cm'bs iron rods should 


Fig. 52. —Shoes for Sinking Well-curbs. 

extend from the shoe well up into the masonry. For large wells, pump- 

pits, etc., heavy iron shoes are often employed, and occasionally a 

pneumatic caisson is found necessary. 

The lining or curb usually consists of a circular wall of brick or 

rubble masonry of a thickness varying with diameter and depth of the 

well, but ranging ordinarily from 2 to 5 feet. Dry rubble may be used 

for the lower portion, but the upper portion should be laid in cement,. 

or at least have a lining so laid, to prevent the entrance of imperfectly 

filtered surface-water. If the well is to be fed from strata that are 

partly or wholly cut off by the curbing, entrance for the water should 

be provided for by laying the wall dry or by means of special openings. 

% 

The entrance of fine sand through such openings can be prevented by 
a back filling of broken stone and gravel suitably graded in fineness. 
A lining of cast-iron segments bolted together has been frequently 
employed in sinking deep wells, especially in Europe, where wells of 
5 to 10 feet in diameter and 75 to 100 feet deep are quite common. 

All wells should be covered to exclude the light and to prevent 
pollution of the water. The cover is usually made of wood, which for 
large wells may be conveniently made of a conical form and supported 
by a light wooden truss, or by rafters resting against the wall. 



r~T 

























































^84 WORKS FOR THE COLLECTION OF GROUND- WA TER. 

324. Yield.—The actual yield of large wells which are considered 
successful varies from 100,000 to 4 or 5 million gallons per day, the 
higher values being very exceptional. A computation of the carrying 
capacity of ordinary porous material by the methods explained in a 
preceding chapter will show that for a single well to furnish one million 
gallons per day requires a very extensive tributary area and a con¬ 
siderable lowering of the water-level in the well. 



Fig. 53.— Large Well at Addison, N. Y. 

(From Engineering News , vol. xxxm.) 


325. Examples. —At Peoria, Ill., a well 36 feet in diameter was sunk on 
ia wooden shoe with cast-iron cutting edge to a depth of 44 feet through clay 
to a water-bearing gravel. During sinking, from 11 to 13 million gallons per 
day were pumped. The curb is a 30-inch brick wall.* 


* Eng. News, 1892, xxvm. p. 26. 





















































































































































































































SHALLOW TUBULAR WELLS . 


285 


At Webster, Mass., a well 25 feet in diameter was sunk in gravel to a 
depth of 30 feet, sheet-piling being driven on the outside of circular ribs made 
of 3-inch plank bolted together. Two sets of piling were used. The curb 
was built as a dry rubble wall 5 feet thick at base and 2 feet thick at top, 
with a 12-inch brick lining laid in cement. Two 6-inch centrifugal pumps 
were used during construction, the maximum pumpage being 1 million 
gallons per day. The cost complete was $13,190.* 

At Addison, N. Y., an auxiliary supply was obtained from a well 12.5 
feet in diameter and 23 feet deep. Fig. 53 illustrates clearly the method 
there used in sinking. On account of very soft material the well was stopped 
short of the necessary depth and the water-bearing stratum was reached by 
twenty-three i-^-inch tubes driven from 7 to 20 feet below the bottom of the 
well. The yield was 165,000 gallons per day. The curb is a 20-inch wall 
in cement, and the cover is of flagging laid on I beams. The cost was, for 
the excavation $2.18 per cubic yard, and for the masonry $5.82. The total 
cost was $851. 

Shallow Tubular Wells. 

326. Shallow tubular wells or wells of small diameter, also called 
driven wells, + are sunk in various ways, depending upon the size and 
depth of well and nature of the material encountered. As wells for 
public supplies would rarely be sunk in rock except to a considerable 
depth, the methods of construction here considered will refer only r to 
shallow wells sunk in soft material. To furnish large quantities of 
water it usually requires a number of wells, and in addition to the 
question of sinking, questions of arrangement, spacing, connecting, 
and operation are important. While the strata penetrated by shallow 
wells are often artesian in character, yet this fact is of little consequence 
in this case, as the pressures would be small and the method of con¬ 
struction and operation the same as for wells tapping the ordinary 
ground-water. 

327. Methods of Sinking.—As regards methods of sinking there are 
two principal kinds of wells: the closed-end well or driven well proper, 
and the open-end well. 

328. The Closed-end or Driven Well. —In this form the well-tube 
consists of a wrought-iron tube from 1 to 4 inches in diameter, closed and 
pointed at one end, and perforated for some distance therefrom. The 
tube thus prepared is driven into the ground by a wooden maul or 
block until it penetrates the water-bearing stratum. The upper end is 
then connected to a pump and the well is complete. Where the 

* Jour. New Eng. W. W. Assn., 1895, ix. p. 240. 

f The term “ driven well ” is somewhat loosely applied to small tubular wells of all 
kinds where the tube is sunk largely by driving. It is also used in a more restricted 
sense to denote a closed-end well sunk wholly by driving and without the removal 
of any material. 






286 WORKS FOR THE COLLECTION OF GROUND-WA TER. 


material penetrated is sand the perforated portion is covered with wire 
gauze of a fineness depending upon the fineness of the sand, d o pre¬ 
vent injuring the gauze and clogging the perforations, the pointed end 
is usually made larger than the tube, or the gauze may be covered by 
a perforated jacket. 

Fig. 54 shows a common form of well-point and a method of driv^ 
ing wells by means of a weight operated by two men. The tube may 



Fig. 54. —Well-point and Driving-rig. 


also be driven by a wooden block operated by a pile-driver or other 
convenient means. 

The well above described is adapted for use in soft ground or sand 
up to a depth of about 75 feet, and in places where the water is thinly 
distributed. On account of the ease with which it can be driven, 
pulled up, and redriven, it is useful in prospecting at shallow depths, 
and in fact groups of wells are often finally located by driving and 
testing until a good result is obtained. 

329. Open-end Wells. —For use in hard ground and for the larger 
sizes the open-end tube is better adapted. This is sunk by removing 
the material from the interior, and at the same time driving the tube 
as in the other case. A very common method of sinking is by means 
of the water-jet. In this process a strong stream of water is forced 
through a small pipe inserted in the well-tube, the water escaping in 
one or more jets near the end of the pipe. At the same time the pipe, 
which is provided with a chisel edge, is churned up and down to 
loosen the material, which is then carried to the surface by the water 
in the annular space between the pipe and tube. If the material is 
hard or the well deep, a steel cutting-edge may be screwed on to the 
end of the well-tube. 

Fig. 55 shows an outfit used by Mr. L. L. Tribus, Mem. Am. Soc. 

















SHALLOW TUBULAR WELLS. 


287 


C. E., in jetting down 6-inch wells at Pensacola, Fla., to a depth of 
90 to 130 feet.* 

The driving was done by a hammer weighing 1000 pounds and 
operated by a pile-driver. The jet-pipe was worked under a water- 
pressure of 75 pounds and churned up and down by a rope led over 
the head of the pile-driver and wound on another spool of the pile- 
driver engine. One engineman, one driller, and two laborers operated 
the machine, and with this force 6-inch pipes were driven 140 feet in 
ten hours. 

A process similar to the water-jet has been used in which steam is 
employed instead of water. Another method is to remove the material 
by means of a sand-bucket. 

Extra-strong pipe, called drive-pipe, is ordinarily used for well- 
tubes, care being taken that the joints are screwed up so that the ends 
of the pipe are in contact. 




Fig. 56.— Cook Well-strainer. 


330. Strainers.— With the open-end well the lower portion may be 
merely perforated with small holes in case the material is coarse or 
gravelly, or if sand is met with, the holes may be covered with brass 
gauze. Instead, however, of using a gauze it is common with this 
style of well to sink a solid tube, insert a special strainer of suitable 
length, and then withdraw the tube nearly to the top of the strainer. 
If necessary a tight joint can then be made between the tube and 
strainer by means of a short piece of tubing cut to a bevel. 


* Eng. Record , 1898, xxxvii. p. 42S. 




































































283 WORKS FOR THE COLLECTION OF GROUNO- WA TER. 


Fig. 56 illustrates a commonly used form of strainer known as the 
Cook strainer. It is made of brass tubing and provided with very 
narrow, slotted holes, which are much wider on the interior than on 
the exterior, an arrangement intended to prevent clogging. 

In some waters the wire gauze has given trouble by rusting up, 
necessitating removal and cleaning. Small perforations in ordinary 
pipe are also apt to give trouble by rusting. This has been avoided in 
some cases by bushing the holes with brass, and in other waters 
galvanized pipe is more successful, the holes being drilled and reamed 
before galvanizing. In fine material a method in successful use in 
wells of large diameter (8 to 12 inches) is to insert a coarse strainer of 
small diameter, fill between strainer and tube with coarse sand, and then 
draw up the tube. In very fine material two or three layers of sand of 
graded size can be used so as to effectually prevent clogging and filling of 
the well. A removable basket-strainer has also been used with success. 

The length of the strainer or perforated portion, in order to reduce 
the friction in the ground to a minimum, should be equal to the thick¬ 
ness of the porous stratum passed through, 
but the resistance to flow will be but 
slightly increased if it is made materially 
shorter, even half or one-third the thick¬ 
ness. The area of the perforations should 
be sufficiently large to keep the velocity of 
entrance down to 2 or 3 inches per second, 
both to keep the friction low and to pre¬ 
vent the entrance of sand. Sometimes 
open-ended tubes without perforations are 
employed, and in the case of thin strata 
the yield may be nearly as great as with 
perforated tubes. With thick strata, how¬ 
ever, the resistance to entrance would be 
greatly increased if all the water is forced 

M^Gra^/ and Sand to enter at the bottom. 

33 i* The Dollard Well .—A form of 
well possessing advantages of durability 
and freedom from clogging is illustrated 
in Fig. 57.* A strainer of vitrified pipe 
is inserted within a temporary casing, the 

annular space then filled with gravel and 
Fig. 57.—The Dollard Well. ou t s ide casing withdrawn. 









Eng. News, 1896, xxxv. p. 114. 

































SHALLOW TUBULAR WELLS . 


289 


332, General Method of Operating a Well System,—Small tubular 

wells are usually arranged in one or two rows alongside a suction-pipe 
and connected thereto by short branches. The smaller sizes are con¬ 
nected directly to the branch, the well-tube acting also as a suction- 
pipe, but with the larger sizes a separate suction-pipe is ordinarily 
employed. In the former case, to avoid the entrance of air, it is 
necessary that the perforated portion of the pipe be always under water, 
and to insure this being the case it should be kept below the limit of 
suction. With the latter arrangement there are no such limitations to 
the position of the perforated well-casing. 

Since the amount of water that can be pumped from a given system 
of wells increases with the amount that the water-level is lowered (up 
to the point where the water-level is reduced to the bottom of the 
water-bearing stratum), and as this is limited by the limit of suction, it 
is always desirable to make the connection between wells and pumps 
at least as low as the pumps. In many cases, to increase the yield 
the suction-pipe is laid at a considerable depth in the ground, and the 
pumps are lowered accordingly. This of course increases the 
expense of construction, and as the height to which the water is 
pumped is increased, it also adds to the cost of operation. The 
most economical design can be arrived at only by a due consideration 
of all these elements. 

The effect of an extreme amount of lowering is apt to be a some¬ 
what serious matter in causing the drying up of wells and springs and 
even of streams, and recent court decisions indicate that a city cannot 
draw too greatly upon the ground-water without rendering itself liable. 

333. Arrangement and Spacing of Wells. The most favorable 
arrangement for a system of small wells is in a line at right angles to 
the direction of flow of the ground-water, as in this way the largest 
possible area will be drawn upon. By placing the wells across the line 
of flow or along a ground-water contour, the advantage of equal heads 
in the several wells is also secured. Where but a small area or width 
needs to be drawn upon, the arrangement is not so material, as the 
water will flow towards the wells from all directions; but with a long 
line of wells and a large draft it becomes a question of much impor¬ 
tance. The amount of water which can be obtained from a system of 
wells depends upon the average amount which the water-level can be 
lowered along the line of wells. The ground-water surface through a 
line of wells when in operation will have some such form.as shown in 
Fig. 58, A , B , C, and D being the wells, LM the original level of 
ground-water, and N 0 P Q R, etc., the new surface. The yield will 


2 Q 0 WORKS FOR THE COLLECTION OF GROUND-WATER. 

be some function of the average lowering h. If intermediate wells,. 
E } F, and G, are inserted and pumped to the same level as the others, 
the surface will be N O' P, etc., the average lowering now being /V, 



Fig. 58.—Section through Line of Wells. 


and more water will be extracted with the same amount of suction; 
but if the circles of influence of the first wells already intersect, the 
additional amount drawn from the intermediate wells will be much less 
than the yield from the others. 

The maximum amount of water obtainable from a given number of 
wells would be when they are spaced far enough apart so that their 
. circles of influence will not overlap, but on account of cost of piping, 
and loss of head by friction, this would not be the most economical 
spacing. If wells are deep and therefore expensive, they should be 
spaced to interfere comparatively little; if shallow, then closer. As 
indicating what the mutual interference of wells may be, the examples 
given on page 278 are of some value. In practice the extent of this 
interference can best be judged by pumping tests of trial wells or of 
those first sunk, the wells being operated at different rates and in 
various combinations. The information thus obtained, together with a 
knowledge of items of cost, will enable the best spacing of subsequent 
wells to be determined. 

While it is impossible to give figures which would be of general 
application, it may be stated that from 25 to 100 feet is about the range 
for economical spacing of shallow wells. With very deep or artesian 
wells the spacing becomes still greater. Spacing less than 25 feet has 
quite often been used, but with doubtful economy. 

The principles here discussed relating to arrangement and spacing 
have frequently been overlooked in the location of small wells, and 
many instances exist where they have been placed in such a way that 
a small part of the actual number would furnish as much as the entire 
group. In one case seventeen 3-inch and 6-inch wells were placed in 
an area within a circle 125 feet in diameter, and a pump test showed 
that seven would furnish as much water as the entire seventeen. In 
another case six 4-inch wells were placed in a row 10 feet apart, and 
a test showed one well to furnish half as much as the six. In still 









SHALLOW TUBULAR WELLS. 


29I 


another case twenty-four 2-inch wells were placed in an area 20 feet 
by 95 feet. Wells so placed that they do not extend the general circle 
of influence do not add to the flow. 

334. Size of Well.—It has been shown (Art. 309) that the effect 
upon the yield of a considerable change in size of well is very small 
provided that the head lost by friction in the well-tube is small. A 
well should therefore be large enough to keep the friction loss within 
low limits, but beyond this little advantage is gained by further 
increase. The proper size thus depends upon the quantity obtainable 
per well, and this in turn upon the spacing. The size and spacing 
should therefore be considered together. With the shallow wells under 
consideration the slight additional cost of the larger well will make it 
economical to keep the friction-head down to a few inches or at most 
1 or 2 feet, corresponding to velocities not exceeding 2 or 3 feet per 
second. A low friction-head, besides making the pumping more 
economical, also increases the suction limit of the pump and hence the 
capacity of a given number of wells. For estimating frictional losses 
for different sizes of wells, use may be made of Table No. 55, page 
276. 

In many cases the best size and spacing are largely influenced by 
the means available for sinking the wells. 

335. As illustrating the relation between size and spacing, reference may 
be made to the various plants of the Brooklyn Water-works.* Some of the 
driven-well plants of these works yield 20,000 to 40,000 gallons per day per 
well from 2-inch wells about 50 feet deep and spaced about 13 feet apart in 
two rows. If a much, wider spacing were adopted and a larger quantity per 
well expected, it would manifestly be necessary to use at least a 3-inch well, 
or else a great loss of head would result. Another plant yields about 200,000 
gallons per well from 6-inch wells (4-L-inch suction-pipes) spaced 40 feet 
apart, a yield which would be impossible from 2-inch wells. To procure the 
same vield from 2-inch wells with the same friction-head would require about 
seven times as many wells, but with a closer spacing a less lowering of water 
in the well would be required, so that for the same total loss of head perhaps 
five times as many wells spaced 8 feet apart would be equivalent. This w r ould 
probably be a more expensive arrangement than that with the larger wells. 
A still more economical arrangement than the one used might be to space the 
wells say 100 feet apart, using 6-inch suctions and 8-inch wells. 

336. Details of Connections.—Each well should be connected to the 
suction-main by means of a short branch in which should be placed a 
gate-valve, so that any well can be shut off at any time. Where the 
well-tube itself is connected to the main it has been found convenient 
to insert a short piece of lead pipe to allow of easy adjustment, as the 


* Brooklyn Water-supply, Department of City Works, 1896. 





292 WORKS FOR THE COLLECTION OF GROUND-WA TER . 

well is likely to be slightly out of plumb. Connection should be made 
at the well by means of a curved T, from the vertical branch of which 
the well-tube should extend to the surface and there be capped. This 
arrangement makes the well readily accessible for inspection and 
cleaning purposes. To reduce friction as much as possible, the con¬ 
nection of branch to main may be made with a Y branch instead of 
a T. The main suction-pipe is usually made of flanged pipe, as this 
enables air-tight joints to be more readily made, although ordinary 
bell-and-spigot pipe with lead joints has been successfully used. 

The greatest care must be taken in every part to make the work 
air-tight, and to secure this it should be thoroughly tested in sections 
by means of compressed air. All valves should be carefully tested for 
air-tightness, and all screw connections thoroughly fitted. Mr. Free¬ 
man C. Coffin in certain specifications * prescribes that the suction- 
main, and branches up to the valves, shall be tested by air at a 
pressure of 50 pounds per square inch, which pressure once secured 
shall be maintained without pumping. The valves are tested under 
100 pounds pressure. 

If settling of main is feared, special foundations must be provided. 
Main and branches are usually laid underground, both for protection 
and to increase the range of pump-suction. The pipe system should 
be made of sufficient size, and all connections so designed as to reduce 
the friction to the lowest limits consistent with economy. This will 
require the use of velocities not exceeding 1 or 2 feet per second. 
The suction-main should be laid on a slightly ascending grade toward 
the pump to prevent lodgment of air at any point. All perforations in 
suction-pipe, or in well-tube used as such, should be below the limit 
of suction. 

337. Air-separator .—In spite of the most careful construction, air 
will usually accumulate to some extent, and to eliminate it many plants 
are provided with air-separators placed on the suction-main near the 
pump. The simplest form consists of a large drum of wrought iron 
through which the water passes at a slow velocity and in a thin sheet 
either over broad horizontal surfaces or over several weirs, in order to 
promote the escape of air. To this drum a vacuum-pump is attached, 
which in some cases is arranged to work automatically. Some plants 
are successfully operated without a separator. 

338. Sand-box .—Where sand is drawn up with the water it may 
be got rid of by passing the water at a slow velocity through a large 

* Quoted in Goodell’s Water-works for Small Cities and Towns, p. 119. 








SHALLOW TUBULAR WELLS. 293 

drum or box inserted in the suction-pipe and provided with suitable 
hand-holes for cleaning. 

339. The Clogging of Wells by filling with sand or by corrosion of 
the screen is a frequent occurrence and may reduce the yield very 
greatly. Wells may be readily cleaned of sand by means of the sand- 
pump or bucket, but if the strainers are corroded they must be pulled 
up, cleaned or renewed, and replaced. If the clogging is due to line 
sand collecting about the outside of tube, it may be removed to some 
extent by forcing water into the wells under high pressure, or by the 
use of a hose, or by means of a steam-jet. Sometimes instead of the 
yield of a well becoming less through continued operation it is actually 
increased, owing probably to the gradual removal of the finer material 
immediately surrounding the well. 

340. Tests.—Besides the preliminary tests already mentioned for 
determining the character of the strata, slope, and flow of ground- 
water, spacing of wells, etc., a tube-well system should always on 
completion be subjected to a thorough test as to capacity. Such tests 
should be continued until the ground-water level has reached a state 
of equilibrium as determined by careful observations at the wells and 
at various distances therefrom. If possible the tests should extend 
over the dry months of the year, and where the system is built by 
contract to supply a certain amount of water, the successful operation 
of the works for a year under a definite head should be a prerequisite 
to final acceptance. If the quantity pumped is large in proportion to 
the capacity of the ground, a long time will elapse before the ground- 
water will cease to fall. The case mentioned on page 279 is instruc¬ 
tive in this connection. 

341. Yield.—The maximum possible yield of a ground-water source 
would be when the entire flow is utilized. With a system of wells this 
can be accomplished only in case the water can be drawn to the bottom 
of the porous stratum, or can be drawn so low that there is no head to 
cause flow away from the wells on the lower side. If the wells are 
located near a body of water and the level of the water in the wells 
is kept as low as that of the surface-water, the entire flow will then be 
utilized. In special cases an artificial dam can be constructed and a 
line of wells or a gallery placed above, as at Daggett, Cal. (Art. 
357). Ordinarily, however, only a part of the flow is intercepted, the 
proportion depending upon the actual lowering compai ed to the maxi¬ 
mum as above explained. 

The actual yield in any case will depend of course upon the condi¬ 
tions relative to the ground-water 5 but where these conditions have 


294 


WORKS FOR THE COLLECTION OF GROUND-WATER. 


been favorable, as at Brooklyn, yields of 300,000 to 500,000 gallons 
per day per 100 feet of suction-main are common.' At Plainfield the 
yield is about 250,000 gallons per 100 feet. Conditions are often less 
favorable than at these places, and yields are likely to be much less; 
but if the ground-water is distributed so thinly that the yield would be 
but 20,000 to 30,000 gallons per day per 100 feet, the cost of suction- 
main, wells, land, etc., would render a ground-water project very 
expensive. It would, however, be rarely possible in such a case to 
find water-bearing strata sufficient in extent to furnish any except very 
small supplies. 

342. Examples. —The tubular-well system at Plainfield, N. J., is an 
example of a very successful plant (Fig. 59). It consists of twenty 6-inch 




Fig. 59. —Tubular Wells at Plainfield, N. J. 


wells of perforated pipe, open at the lower end and provided with separate 
44-inch suction-pipes. The wells are from 35 to 50 feet deep, and are sunk 
into a coarse water-bearing gravel overlaid by clay. They are spaced about 
50 feet apart and are connected to the suction-main by 5-inch branches. 
The suction-main varies in size from 8 to 12 inches. The ground-water at 
this place has a slope of about 3 feet in 1900, indicating a copious flow. 
A 24-hour pumping-test indicated a yield of about 150,000 gallons per day 
per well with ten wells connected, and a depression of water-level of only 


































































SHALLOW TUBULAR WELLS. 


2 9 5 


2 feet. At 700 feet distant the lowering in a test well was 0.6 foot. With 
more wells operated the yield per well was less. From Table No. 55, page 
276, it is seen that the size of the well is none to' great for the yield. Fig. 
59 shows the arrangement of wells and details of well and manhole. The 
cap of the well is tapped for a vacuum-gauge connection.* 

A very economically constructed system is that at Brookline, Mass. The 
wells, of which there are 160, are 2\ inches in diameter and from 35 to 95 
feet deep. They are open at the bottom and perforated for the lower 2 feet, 
the holes being bushed with §-inch brass pipe. They are arranged along a 
suction-main about 6000 feet long. Each well is connected to this main by 
means of two short pieces of lead pipe between which is placed a gate-valve. 
The cost of driving and connecting up 118 good wells averaging 50 feet deep, 
including work done in driving and pulling up 41 unsuccessful wells, was 
$47.90 per well. The average rate of driving with four men was 50 feet per 
day, at a cost of 21 cents per foot for labor, f 

The city of Brooklyn, N. Y., obtains a large proportion of its water- 
supply from small wells. In 1895, of the total supply of about 75 million 
gallons, about 35 million was from wells, and an additional well-supply of 25 
million gallons was contracted for. The old wells are nearly all of the small 
closed type and are grouped at six stations. Fig. 60 shows a plan of one of 



Fig. 60.—Forest-Stream Driven-well Station, Brooklyn, N. Y. 

these older stations. J The arrangement is quite similar in all, the wells 
being placed in two rows, one on each side of the suction-main. The later 
plants are to consist of open wells perforated and covered with screens, with 
suction-pipes placed inside. A description of one of the new plants is as fol¬ 
lows: The main suctions are about 2340 feet long with a fall of 12 inches 
from centre to each end. The 62 wells are staggered along the main suction- 
pipe, 12 feet from it and 75 feet apart on each side.. Their average depth is 
45 feet, a stratum of fine sharp sand being met with at that depth. The 
outside casing is 4-J- inches, with 6-foot strainer, 2-foot sand-pocket, and 
6-inch point. Suctions are 3 inches in diameter and 28 feet long. Lateral 
branches are 3F inches, and each is provided with a gate. It is expected to 
get 6 million gallons from this station. The contract price for the last 25 
millions was $167,250 for sinking and connecting wells, the yield to be 
determined by a test lasting one year and taken as the lowest average for five 
consecutive days. 


* Trans. Am. Soc. C. E., 1894, xxxi. p. 371. 
f Jour. New Eng. W. W. Assn,, 1897, XI. p. 196. 
\ Brooklyn Water-supply, Plate 25. 


* 











296 WORKS FUR THE COLLECTION OF GROUND-WATER. 


Deep eind Artesian Wells. 

343. Comparison with Shallow Wells.—Where the depth exceeds 
75 to 100 feet the small driven well is no longer practicable. The 
expense of construction per well now becomes much greater, prelimi¬ 
nary investigation much more difficult, and the problem altogether 
requires more careful consideration. Fortunately the deeper strata are 
usually more uniform and of greater extent than strata near the surface, 
so that in regions already explored deep wells can be sunk with far 
more certainty of success than is usually the case with shallow wells. 
Methods of sinking deep wells are in many respects different from those 
already described, and matters of spacing, pipe-friction, arrangement 
of connections, etc., are much more important than in the shallow- 
well plant. 

344. Boring Deep Wells.—Well-boring is an art by itself, and the 
execution of any deep-well project should usually be put into the hands 
of some reliable well-drilling concern. The variety of ingenious tools 
and appliances in use for overcoming all kinds of difficulties and for 
penetrating all sorts of strata is very great, and it is possible to give 
here but a very general description of some of the methods of sinking 
in use. The methods used for soft and for hard materials are very 
different, and the subject will be divided accordingly. 

345. Sinking of Wells in Soft Materials .—In soft material it is of 
course necessary to case the well the entire depth, and on account of 
the difficulty of getting the casing down to great depths this operation 
becomes the chief feature of the construction. 

For depths up to 200 or 300 feet the ordinary well-drilling outfit 
can be used, and the casing driven close after the drill. By the use of 
an expansive drill the hole can be made slightly larger than the 
casing, thus making it possible to drive the casing much farther, and 
even enabling strata of soft rock to be passed. When the casing can 
be driven no farther a smaller size is inserted and the sinking continued 
with a smaller drill, and so 011 until the well is sunk as far as desirable 
or possible. The material excavated is brought to the surface by 
means of a sand-bucket, or by the water-jet as previously described 
in Art. 329, the water being conducted to the end of the drill through 
hollow drill-rods. By the latter method the hole is kept clean and" a 
more rapid progress made. 

The friction against the casing is greatly lessened, and the depth 
attainable much increased by the use of the revolving process. In this 
the lower end of the casing is provided with a toothed cutting-shoe of 


DEEP AND ARTESIAN WELLS. 


297 


hard steel of slightly greater diameter than the pipe, and the upper end 
is connected by means of a swivel to a water-pipe through which water 
is forced by suitable pumps. I he well is bored by turning the pipe, 
and the loosened material is carried to the surface by the water which 
passes down inside the casing and up on the outside between casing 
and soil. So long as the water-pressure is maintained there is very 
little friction between the earth and the pipe, and the tube is readily 
rotated and sunk at the same time. This process is very common in 
sinking artesian wells in the alluvial basins of California. It is very 
rapid, a rate of sinking as high as 20 or 30 feet per hour for depths of 
1000 feet having been attained. 

It is essential to have a good length of strainer in the porous 
stratum. This is usually inserted after the desired depth has been 
reached, and the casing is then pulled up to the top of the strainer. 
By special devices it can, however, be attached to the end of the well- 

t 

casing and sunk with it. 

346. Examples. — At Memphis, 8-inch wells were sunk by the jetting pro¬ 
cess. A 10-inch well was first sunk 70 to 90 feet to clay to cut off undesirable 
water, and the 8-inch pipe was then forced down by means of an hydraulic 
jack anchored to the 10-inch pipe. In this way a depth of 600 feet could be 
reached. In one case a 6-inch pipe was continued inside the 8-inch to a total 
depth of 1165 feet. Cook strainers 50 feet long were used, 1 inch smaller 
than the 8-inch casing, and closed at the bottom. After being lowered the 
casing was pulled up nearly to the top of the strainer, and a ring packing of 
rubber and brass driven between strainer and tube.* 

A very deep well was sunk by the revolving process at Galveston, Texas. 
The first casing was 22 inches in diameter and was sunk 57 feet. This was 
followed by 15-inch casing to a depth of 870 feet; then, following this, pipes 
of 12-inch, 9-inch, 8-inch, 7-inch, 6-inch, and 5-inch diameter were used, 
with which a depth of 3067 feet was reached. The contract price was $75,000 
for a depth of 3000 feet. The cost of the plant ready for work was $12,000. 
A water-pressure of 250 pounds per square inch was used in sinking, j* 

347. Boring Wells in Rock. —A drilling outfit for deep wells is very 
similar to the ordinary familiar outfit for shallow wells worked by 
horse-power. A string of tools consists essentially of a steel bit, an 
auger-stem into which the bit is screwed, a pair of links or “jars ” 
connecting the auger-stem with another bar, called a sinker-bar, and 
finally the rope cable which supports the apparatus and which passes 
over a pulley at the top of a derrick and then down to a winding 
drum. Just above the drum the cable is attached, by means of an 
adjusting or “ temper ” screw, to a large walking-beam operated by a 


* Eng. Record , 1891, xxiv. p. 234. 
f Eng. News , 1892, xxvm. p. 122. 




298 WORKS FOR TIIE COLLECTION OF GROUND-WATER. 


steam-engine. As the work progresses the drill is lowered by the 
temper-screw. By means of the jars an upward blow may be struck 
to dislodge a jammed drill. Many ingenious tools are employed for 
recovering lost tools, cutting up and removing pipe, and carrying on 
the various operations involved. 

Wooden poles are sometimes employed to support the drill, but 
this system is not much used in the United States. Its advantage lies 
in the greater command the driller has over the drill, both in turning 
it and in maintaining a straight hole. Its chief disadvantage is in 
the length of time required to remove the drill from the hole. 

In this country deep wells are almost invariably of small diameter. 

In Europe, however, deep-bore wells are 
frequently constructed of a diameter of 2 to 
4 feet and even as large as 6 feet. One such 
well is the Place Herbert well of Paris, 3J 
feet in diameter and 2536 feet deep.* At 
Southampton, England, two 6-foot wells 
spaced 11^ feet apart were bored in chalk 

to a depth of 100 feet. They were intended 

Fig. 61.—Large Well-boring to serve a l so as pump-pits. The boring 
Apparatus 11 

apparatus used at this place is illustrated in 




Fig. 6i.t 

348. Casing of Wells.—Wells in soft material must be cased 
throughout. When bored in rock it is necessary to case the well at 
least through the soft upper strata to prevent caving. Casing is also 
desirable for the purpose of excluding surface-water, to which end it 
should extend v eil into the solid stratum below. Where artesian con¬ 
ditions exist and the water will eventually stand higher in the well than 
the adjacent ground-water, the casing must extend into and make a 
tight joint with the impervious stratum, otherwise water will escape 
into the ground above. 

A reliable joint can best be made by sinking a smaller tube inside 
the outer one, and filling the space between it and the well or outer 
tube by some form of packing. Rubber packing-rings are used for this 
purpose, which if well placed are very effective. They are hollow 
cylinders of soft rubber inserted in an adjustable length of tubing of a 
diameter smaller than the well, and when lowered to the proper place 


* Eng. News , 1888, XIX. p. 488. 
f Proc. Inst. C. E., xc. p. 33. 















DEEP AND A PTES/AN WELLS. 299 

are expanded to fill the annular space by screwing up the tubing. 
Linseed bags wrapped around the tubing have been much used for 
packing. The seed expands as it becomes water-soaked and so fills 
the space. Lead packing has also been used with satisfactory results. 
It is first cast around the end of the pipe, the pipe lowered in place, 
and the joint made by driving the pipe firmly into the hole, which has 
previously been reamed out smooth. 

If two or more water-bearing strata are encountered, the water- 
pressures in the different strata are likely to be different, that from the 
lower usually being the greater. If it is desired to utilize only the 
water from the lower stratum at its maximum head, it will be necessary 
to place the packing in the impervious stratum immediately overlying 
the one in question. Otherwise the head attained will be more nearly 
that of the upper strata. Where different pressures thus exist it is only 
possible to determine their amount by separately testing each stratum 
as reached, the others being cased off. This operation is an essential 
part of the boring and should be carefully performed. Important differ¬ 
ences in quality are also often discovered in this way. 

In placing permanent packing it does not necessarily follow that 
certain strata should be excluded because of a less static head than 
others. None need be excluded from which the head is greater than 
the head existing at the level of the stratum when the works are in 
operation. The question therefore depends upon the amount it is 
proposed to lower the water by pumping. 

Ordinary artesian well-casing is made of light-weight wrought-iron 
lap-welded pipe. For pipe which is to be driven the standard 
wrought-iron pipe is ordinarily used, but for heavy driving extra-strong 
pipe is necessary. Joints of drive pipe should be made so that the 
ends of the tubing are in contact wheri screwed up. 1 he life of a good 
heavy pipe is ordinarily very great, but cases have occurred where the 
pipe has been rapidly corroded, due to the presence of excessive 
amounts of carbonic acid. 

349. Cost.—The cost of sinking wells will of course vary greatly 
according to locality, nature of strata, and depth and size of well. 
For wells 6 to 8 inches in diameter and sunk in ordinary rock the cost 
per foot, not including casing, will usually range from $2.00 to $3.00. 
.for depths of 500 feet, up to $3.00 to $5.00 for depths of 2000 feet.. 
For smaller sizes the cost will be somewhat less, especially for the 
shallow depths. In the Dakotas 2-inch wells have been sunk 285 ieet 
for 42 cents per foot, and forty-two such wells with an average depth 


300 WORKS FOR THE COLLECTION OF GROUND-WATER. 

of 322 feet had an average cost of 78 cents per foot. Six-inch wells 
cost from $5.00 to $6.00 per foot complete for depths of 500 to 
1000 feet.* 

In soft material the cost for small depths will be somewhat lower 
chan in rock, but for great depths much higher, on account of the 
difficulty of sinking. 

For sizes much exceeding 12 inches the cost will rapidly increase. 
The cost of the large 6-foot wells at Southampton already referred to 
was about $25.00 per foot for boring, and $20.00 for casing. 

350. Arrangement.—The best arrangement of deep wells is in a 
straight line at right angles to the line of flow, but the latter point is 
of much less importance than with shallow wells in a limited water¬ 
bearing stratum; as, owing to the lateral extent of the strata and slight 
inclination of the hydraulic grade-line, water will flow towards a small 
group of wells nearly equally from all directions. 

351. Size and Spacing.-—The high cost of deep wells renders a 
thorough preliminary investigation relative to proper size and spacing 
impracticable, but for the same reason a correct determination of these 
points is of great importance. The desired knowledge must be got by 
a study of similar plants, or gained as the sinking of the wells pro¬ 
gresses. 

To be able to draw correct inferences from tests of artesian wells it 
is very essential that water from the upper strata be carefully excluded. 
Static heads can then be measured by allowing the water to rise in. an 
open pipe, or by means of a gauge. The difference between this static 
head and the head measured when the well is flowing or being pumped 
from is then partly consumed in overcoming friction in the well and 
partly in forcing water into the well through the porous strata. The 
effect of a change in size of well and of head can then be readily 
estimated, in accordance with the principles of Art. 311. As a valu¬ 
able aid in such calculations the flow at different heads should be 
determined and a discharge curve drawn. This gives directly the 
effect of variation of head in the particular well tested, and also enables 
the matter of friction to be more accurately determined. 

The economical spacing for deep wells will be much greater than 
for shallow wells. It will likewise pay to spend much more money in 
lowering the flow-line by making deep connections, thus decreasing 
the number of wells and increasing the spacing. The questions of 
size, spacing, and connections are interdependent, and also depend 


* Eleventh Census, Report on Agriculture by Irrigation. 





DEEP AND ARTESIAN WELLS. 


301 


upon the economy of different types of pumps; and a correct solution 
requires a careful study of these questions, together with many others 
depending upon local conditions. It will often be necessary to estimate 
on several different arrangements before the best one is arrived at. 

Spacings in some carefully constructed works which have apparently 
given satisfactory results are: At Galveston, Texas, thirty 7-inch 
wells, about 800 feet deep and 560 feet apart, yield about 250,000 
gallons per well. At Memphis, forty-two 6- and 8-inch wells about 
400 feet deep were spaced at first 75 feet apart and afterwards 250 feet. 
Maximum flow — about 250,000 gallons per well. At Savannah, Ga., 
12-inch wells 500 feet deep were spaced 300 feet apart. Yield = 
about 800,000 gallons per day per well. At Galveston, the connec¬ 
tions were made at a slight depth below the surface; at Memphis, in a 
tunnel 80 to 90 feet deep; and at Savannah, in a conduit 20 feet deep. 
At Fort Worth, Texas, thirteen 8-inch wells 1000 feet deep were placed 
800 feet apart. The total yield was about 1,000,000 gallons, although 
the first two or three wells indicated a total of 3,000,000 gallons. 

352. Methods of Operation.—On account of the relatively great cost 
of deep wells it will often be found economical to so arrange the pumps 
and connections that a considerable lowering of the water-level below 
the ground-surface may be obtained. This is generally accomplished 
by connecting all the wells to a single pump or set of pumps, placed 
at a greater or less depth below the surface. Where the connections 
are very deep tunneling may have to be resorted to. Another 
common method of drawing water from deep wells in the case of small 
plants is by the use of a separate deep-well pump for each well. This 
method is applicable to any depth, but involves the use of uneconomical 
types of machinery. The air-lift is another form suited to this work. 
(For further discussion of the question of pumping machinery see 
Chapter XXVI.) 

353. Examples of Artesian-well Plants.—In the majority of cases an 
artesian-well plant, where consisting of several wells, is operated in the same 
way as a system of shallow wells, a good illustration of which is the Plainfield 
works described on page 294. Two noteworthy exceptions to this arrange¬ 
ment are the large works at Memphis, Tenn., and at Rockford, Ilk,—plants 
which represent the most modern practice in this branch of water-works 
engineering. 

The supply at Memphis is obtained from a series of forty-two wells sunk 
about 400 feet deep to a stratum of water-bearing sand. Little natural flow 
was obtained, and, to increase the yield, the pumps were located in a pump- 
pit about 50 feet deep and connections made with the wells by means of 
tunnels. Vertical compound engines were adopted having a duty of about 


302 WORKS FOR THE COLLECTION 0L GR0 UND-WA TER 


115,000,000 foot-pounds per 1000 pounds of steam.* Mr. T. T. Tohnston 
was the engineer. J 

A later example and one involving several interesting features is the plant 
at Rockford, Ill., Mr. D. W. Mead, Mem. Am. Soc. C. E., engineer. 



Discharge Pipe 



Ran of Shaft Showfao 
Arangement of Engines 



SecHon of Shaft Showinof 
Arrangement of Pump*. 


Vertical Section of Shaft, 

- ^-— vi ■ vi 1 ijjtr 

Fig. 62 —Pump-shaft and Pumps, Rockford, III. 

(Prom Engineering News , voi. xlii.) 

Previous to 1898 the city had been supplied for some years by artesian wells 
part sunk to the Potsdam sandstone and part into the St. Peter (see Fit? 
42> page I04 )- Increased demand necessitated increased lowering of the 


* & 


n g> Record , 1891, XXIV. p. 234. 



































































































































































































































































































































DEEP AND ARTESIAN WELLS. 


303 


water-level, a result temporarily accomplished by means of deep-well pumps 
and bv the air-lift. The arrangement adopted for the new plant was to sink 
a shaft 95 feet deep, place pumps therein, and connect them to the various 
wells through tunnels constructed from the bottom of the shaft. The arrange¬ 
ment is clearly shown in Fig. 62. The shaft is water-tight, with a floor of 
concrete, and the lateral tunnels are filled with concrete, put in after the 
' suction-pipes were placed. The two pumps, each of 3 million gallons 
ordinary capacity, are of the centrifugal type and are operated through rope 
transmission by compound engines placed at the surface. Under a head of 
over 100 feet the pumps alone developed an efficiency of from 70 to 75 per 
cent, and the whole plant a duty of 58,000,000 foot-pounds per 1000 pounds 
of dry steam. For further data regarding these pumps see Chapter XXVI. 

354. Yields.—In making estimates regarding flow it is important 
to bear in mind that it requires a considerable length of time to deter¬ 
mine with certainty the adequacy of the supply, and furthermore that 
the sinking of wells by other interests, even though at considerable 
distances, may very seriously affect the yield. The amount of water 
flowing through a porous rock, per square foot of cross-section, is likely 
to be very much less* than that which is often found in coarse sand and 
gravel strata. The slope of the hydraulic grade-line in the former case 
is usually very much less and the friction much greater, large volumes 
depending on great thickness and breadth of strata. Detailed figures 
relating to yield for several supplies have been given on page 301. 
Where conditions are sufficiently favorable for works of some magni¬ 
tude the yield per well under a moderate head ranges from about 
150,000 gallons per day to 800,000 gallons, or even more. With 
yields of less than 100,000 gallons per day, works for developing large 
quantities become very expensive, relatively more expensive than for 
small quantities, since with a large number of wells there is much 
greater interference. 

355. Failure of Wells.—The chief cause of a decrease in yield of a 
well is the influence of other wells sunk in the vicinity. This effect is 
likely to be felt much farther than when similar quantities are drawn 
from gravel strata, on account of the great depth to which the head, 
or flow-line, is often reduced in deep wells by pumping. The case 
of the failure of wells in the vicinity of Chicago, and its effect for 
several miles around, has already been mentioned. At Savannah it is 
estimated that the withdrawal of 10 million gallons per day affects the 
pressure for 8 miles distant. At Dubuque, Iowa, a large well bored 
on low ground caused the flow from several wells higher up to cease 
entirely. At Denver the flow has also greatly decreased and varies 
with the season. 

The yield of a well may also decrease on account of causes inherent 


304 WORKS FOR THE COLLECTION OF GROUND-WATER. 

in the well itself. One such cause is leakage due to defective packing, 
this being a common fault of wells in the Dakota basin. Another 
cause of partial failure is by clogging through the inflowing of fine 
sand. This can be removed by the methods described on page 293. 

HORIZONTAL GALLERIES AND WELLS. 

356. Filter-galleries.—Where ground-water can be reached at 
moderate depths it is sometimes intercepted by galleries constructed 
across the line of flow. If these are placed at a sufficient depth they 
will evidently enable the entire flow of the ground-water to be inter¬ 
cepted. In form a gallery may consist merely of an open ditch which 
leads the water away, or it may be a closed conduit of masonry, wood, 
iron, or vitrified clay pipe, provided with numerous small openings to 
allow the entrance of the water. Unless constantly submerged, wood 
should not be used. Masonry and vitrified pipe are preferable to iron, 
as these materials are uninjured by exposure to water. If galleries are 

not covered, excessive vegetable growth is apt to occur which may 

* 

injure the quality of the water. 

Galleries are usually constructed in open trench. To prevent the 
entrance of fine material the back-filling near the openings should be 
of gravel of graded size, and as an additional precaution the openings 
may be made in the bottom only. Manholes should be provided to 
permit of inspection and cleaning. Galleries need be of a size only 
large enough to carry the estimated quantity, or, in case trouble with 
sand is feared, large enough to permit ol inspection. They are 
arranged to lead the water to the pump-well, and may be provided 
with gates so that the water may be shut off from various sections. 

The cost of galleries is about the same as that of sewers in similar 
ground. It increases rapidly with the depth, but up to a depth of 20 
or 25 feet it is sufficiently low that the construction of galleries can 
often be advantageously undertaken. A gallery not only intercepts 
the water more completely than wells, but it replaces the suction-pipe, 
it is more durable than either pipe or wells, and all trouble from the 
pumping of air is avoided. 

357. Examples. —There are comparatively few cases in this country where 
galleries have been used to intercept ground-water proper, they being mainly 
used to collect filtered stream-water as explained in Art. 359. As an example 
of their use for ground-water collectors, mention may be made of the gallerv at 
Naples, Italy. The supply there is taken from a gravel stratum 10 to 13 feet 
thick, overlaid by 30 feet of clay. The gallery is 2000 feet long. It was 
constructed in open trench and back-filled with gravel and clay. The yield is 
38 million gallons per day.* 


* Proc. Inst. C. E., lxxxiv. p. 




F1L TER-GALLERIES. 


30s 

The city of Munich, Germany, gets its water-supply from springs and 
collecting-galleries in the foothills of the Alps. The water occurs in a deposit 
of gravel resting upon a bed of sandstone, and is intercepted by collecting- 
tunnels driven nearly horizontally, and located partly in the sandstone and 
partly in the overlying gravel. From these galleries the water is conveyed to 




Fig. 63.—Collecting-galleries, Munich Water-works. 

(From Engineering Record , vol. xxxvm.) 

an aqueduct leading to the city. Fig. 63 shows the general arrangement and 
an enlarged cross-section of a collecting-tunnel.* * * § 

Karlsruhe obtains its water-supply from an old river-bed filled with gravel. 
The water is impounded by a clay wall or dam and collected by a gallery 
which yields 1,600,000 gallons per day.f 

Many cities in Holland secure their supplies from open ditches and galleries 
in the sand-dunes. Amsterdam collects in this way about 10 inches out of a 
total rainfall of 30 inches per year. Other yields have been obtained as high 
as 20 to 25 inches. 

Galleries have been constructed at several places in the West for collecting 
water from the large gravel deposits beneath and adjacent to the streams. 
Such are the older works of Denver J and of Golden, § Colorado, and Eureka, || 
Cal. These galleries usually consist of wooden boxes or cribs constructed at 
a considerable depth in the water-bearing gravel, and are often arranged to 
collect not only ground-water but filtered surface-water from the streams. 
At Eureka provision is made for back-flushing. 

At Daggett, Cal., water for irrigation is obtained from underground 
streams by means of a flume, the water being dammed up by sheet-piling 
driven across the line of flow. Surface-water flows here also after heavy 
storms. 

358. Tunnels in Rock.—Galleries for collecting ground-water are 
occasionally tunneled in solid rock. This may happen along a side 

* Eng. Record , 1898, XXXVIII. p. 78. 

f [our. f. Gasbel. u. Wasservers ., 1894, p. 269. 

% Trans. Am. Soc. C. E., 1894, XXXI. p. 135. 

§ Eng. News , 1891, xxv. p. 610. 

I) Ibid., p. 339. 

1 Eng. News , 1896, xxxvi. p. 157. 













306 works for the collection of GROUND-wa ter. 


hill where an outcropping porous stratum overlies an impervious one 
and it is desired to develop the flow by running a tunnel along the hill 
near the bottom of the porous stratum; or it may occur where a steeply 
inclined artesian stratum can be more readily reached in this way than 
by vertical wells. Fig. 64 illustrates the conditions at Oakland, Cal., 




4 - Ff7?/ - ■»- \5~0/77/ - - • *k 


DO m/- 


FlG. 64. 

where it is proposed to tap the artesian strata by means of tunnels.* 

Tunnels or galleries are also sometimes run from the bottom of 
large wells for the purpose of increasing the yield. This method of 
increasing the flow is advantageous where it is necessary to lower the 
pumps and to concentrate the flow in a single well. 

359. Wells and Galleries Near Streams. —Wells and galleries are 
often constructed near streams for the purpose of getting all or a por¬ 
tion of the supply therefrom; and, on the other hand, it often happens 
that wells sunk near streams obtain much of their water from them 
when they are supposed to get it all from the opposite direction. In 
general the natural ground-water surface will slope towards a stream 
as shown in Fig. 17, page 85; and until a well is pumped from, the 
water-level therein will stand higher than the surface of the water in 
the stream. The amount the water in the well can now be lowered 
without drawing from the river depends upon the distance of the well 
from the stream and upon the ground-water slope; but no water can 
enter from the river so long as there is a summit in the ground-water 
surface between the stream and well. A few test-borings placed 
between the well and stream will determine this point. The source of 
water can also often be determined by chemical analysis. 

Where wells or galleries are placed near streams for the purpose of 
obtaining surface-water filtered through the ground, the success of such 
works depends much upon the character of the river-bottom. Even 
when the lower strata are porous, the river, if a silt-bearing one, may 


* Eng. Record, 1S95, xxxii. p. 41. 










FILTER-CRIBS. 


307 






have a nearly impervious bottom and the natural filter will only become 
more clogged by use, necessitating perhaps the abandonment of the 
collecting-works. Such failures have occurred in some instances. With 
a sandy river-bottom kept clean by the scouring action of the floods, 
and with a porous substratum, works of this kind will give good results. 
To secure good filtration the works should be located at least 50 feet 
and preferably a greater distance from the stream. Galleries of the 
kind here considered have sometimes been built of great width, but, as 
most of the filtration must be lateral, very little is gained by increasing 
the width over that required for convenience in construction and 
inspection. 

The yield of a series of wells or of a gallery collecting filtered surface- 
water will be, as in the case previously discussed, proportional to the 
lowering of the water-level, or to the head on the filter, and will be 
nearly proportional to the length of the line of works. In gallons per 
day per IOO feet of gallery, the yield from various successful works 
varies from 30,000 to 1,000,000 or more, which is about the same as 
is obtained from lines of wells. 

360. Horizontal or Push Wells are tubular wells pushed approxi¬ 
mately horizontally into a water-bearing stratum, or under the bed of 
a lake or stream. They are forced into the ground from a trench by 
means of jacks braced against the opposite side. These wells have 
been most successful when extended out under a body of water. At 
South Haven. Mich., three 6-inch Cook wells with 30-foot strainers 
were pushed out 150 feet under Lake Michigan. The wells were 25 
feet apart and yielded 1,250,000 gallons per day. Another similar 
plant at Crystal City, Mo., consisted of two 8-inch wells with 65 feet 
of strainer, extending 200 feet under the Mississippi River in a sand 
stratum 20 feet thick. The yield was 1,300,000 gallons per day.* 

361. Filter-cribs,—Another method of utilizing a river-bottom as 
a natural filter is to construct a wooden crib in an excavation in the 
bed of the stream, fill it with graded gravel and then cover the struc¬ 
ture with 3 or 4 feet of sand up even with the river-bottom. The 
suction-pipe then leads from the crib to the pumps. This form of. 
construction is well adapted to sandy-bottom streams with swift cur¬ 
rents and has proved a very efficient way of clarifying muddy river- 
waters. The rate of filtration through such a filter may be quite 
closely estimated according to the principles explained in Chapter 
XXL 


* Eng. News , 1893, xxix. p. 452. 





308 works for the collection of ground-water . 

In Fig. 65 is illustrated a crib at Kensington, Pa., similar to 
several which have been constructed in the Allegheny River. This 
crib is 200 feet long, 32 feet wide, and 4 feet high, and is covered with 


Approximate Low Water Leva 



Fig. 65.—Filter-crib, Kensington, Pa. 

(From Engineering News, vol. xxxi.) 

4 feet of gravel and sand dredged from the river-bottom. It is 
designed for a capacity of 3 million gallons per day, equal to a rate of 
filtration of about 16 million gallons per acre per day. The estimated 
cost is $2400 per million gallons capacity. Provision is made for 
cleaning by back-flushing. The system was designed by Mr. James 
H. Harlow, Mem. Am. Soc. C. E. The cribs are usually placed 
where the velocity of the current is from 4 to 8 feet per second, and 
little trouble has been experienced through clogging. 

Filters of this sort are found to clarify the water at most times quite 
satisfactorily, but the bacterial content of the water is but little 
changed. The hardness is likely to be increased. 

LITERATURE. 

LARGE OPEN WELLS. 

1. Matthews. The wells and Borings of the Southampton Water-works. 

Proc. Inst. C. E., 1886, xc. p. 33. 

2. The New Water-works at Peoria, Ill. Eng. News , 1892, xxvm. p. 26. 

3. Winslow. Water-supply of Waltham. Jour. New Eng. W. W. Assn.,, 

1893, viii. p. 118. 

4. Fuller. A Description of the Water-works at Webster, Mass. Jour. 

New Eng. W. W. Assn., 1895, ix. p. 240. 

5. Labelle. Auxiliary Supply of the Water-works of Addison, N. Y. Eng. 

News, 1895, xxxiii. p. 163. 

6. Sinking a large Supply-well for the Water-works of Canton, Mass. 

Eng. News, 1896, xxxvi. p. 211. 

driven wells. 

1. Noyes. The Driven-well System as a Source of, or a Means of Obtaining, 

a Water-supply. Jour. New Eng. W. W. Assn., June, 1887. Eng. 

Record, 1887, xvi. p. 264. 

2. The Malden Water-works. Eng. Record , 1889, xx. p. 303. 

3. Forbes. Driven Wells as a Source of Water-supply. Tour. New Eng 

W. W. Assn., 1891, v. p. 141. 
























LI TER A TU RE. 


309 


4. The Driven-well System of Schuyler, Neb. Eng. News, 1892, xxvm. 

p. 199. 

5. Extension of the Driven Wells of the Malden Water-works System. 

Eng. Record , 1893, xxvn. p. 399. 

6. The Foxboro, Mass., Water-works. Eng. Record , 1893, xxvn. p. 456. 

7. McElroy. Supply-wells for Brooklyn, N. Y. Proc. Am. W. W. Assn., 

1893, xiii. p. 13. 

8. Tribus. Driven Wells of the Plainfield Water-supply System. Trans. 

Am. Soc. C. E., 1894, xxxi. p. 371. 

9. Bowers. Experiment with Tube Wells at Lowell, Mass. Jour. New 

Eng. W. W. Assn., 1894, ix. p. 67. 

10. Bowers, Description of Second Tube-well Plant at Lowell, Mass. Jour. 

New Eng. W. W. Assn., 1896, x. p. 226. 

11. Hague. Central Water-supply Stations for Railways. Eng. News, 1896, 

xxxv. p. 114. 

12. Forbes. Driven Wells at Brookline, Mass. Jour. New Eng. W. W. 

Assn., 1897, xi. p. 195. 

13. Bowers. Result of Tube-well Experiments in Lowell, Mass. Jour. New 

Eng. W. W. Assn., 1898, xiii. p. 30. 

14. Sinking Driven Wells. Eng. Record, 1899, xl. p. 362. 

ARTESIAN WELLS. 

1. Darley. Artesian Wells. Notes on Drilling and Boring Artesian Wells 

as Practiced in the United States of America. Engineermg, 1885, 
XLI. p. 683. 

2. Tweddle. The Boring and Sinking of Wells. Engineermg, 1888, xlvi. 

p. 199. 

3. The Memphis, Tenn., Water-works. Eng. Record, 1891, xxiv. p. 234. 

4. Irrigation by Artesian Wells. Eng. News, 1892, xxvm. p. 342. Data 

of cost. 

5. St. Augustine’s Artesian Water. Eng. News, 1892, xxvn. p. 182. 

6. The Deep Artesian Well at Galveston, Tex. Eng. News, 1892, xxvm. 

p. 122. 

7. Carter. Artesian Wells. Jour. Franklin Inst., 1893, cxxxvi. p. 230. 

8. The New Artesian Water-supply at Savannah, Ga. Eng. News, 1893, 

xxix. p. 527. 

9. Fort Smith, Tex., Water-works. Eng. Record, 1894, xxx. p. 5. 

10. Carpenter. The Effect of Neighboring Artesian Wells on each Other. 
Eng News, 1895, xxxiv. p, 277. 

xi. The Galveston Water-works. Eng. Record, 1896, xxxiv. p. 122. 

12. Johnston. The Restoration of the Water-supply at Savannah, Ga, 

Jour. W. Soc. Eng., 1897, 11. p. 711. 

13. Johnston, Discussion on Deep-well pumping. Jour. West. Soc. Engrs., 

1897, 11. p. 190. 

14. Jetting Down Artesian Wells. Eng. Record, 1898, xxxix. p. 428. 

15. The Large Artesian-well Plant at Camden, N. J. Eng. Record, 1899, 

xxxix. p. 520. 

16. The New Water-supply System of Rockford, Ill. Eng. News, 1899, 

XLII. p. l8. 


3io 


WORKS FOR THE COLLECTION OF GROUND-WATER. 


FILTER-GALLERIES AND FILTER-CRIBS. 

1. The Naples Water-works. Proc. Inst. C. E., 1885, lxxxiv. p. 468. 

2. The Water-works Extensions at Newton, Mass. Eng. Record , 1891, 

xxiv. p. 418. 

3. The Reading, Mass., Water-works. Eng. Record , 1892, xxv. p. 282. 

4. Horizontal Tubular Wells at South Haven, Mich. Eng. News, 1893, 

xxix. p. 452. 

5. Water-supply of Oakland, Cal. Eng. Record, 1895, xxxn. p. 41. 

6. Lippincott. Water Development on the Mojave River, near Dagget, 

Cal. Eng. News, 1896, xxxvi. p. 157. 

7. Fuertes. The Water-works of Munich, Germany. Eng. Record, 1898, 

xxxviii. p. 78. 

8. Filter-cribs in the Allegheny River, near Pittsburg, Pa. Eng. News, 1898, 

xxxix. p. 269. 

9. The Filter-crib of the Allegheny Water-works. Eng. News, 1900, xliii. 

p. 328. 


CHAPTER XV. 


IMPOUNDING-RESERVOIRS. 

CAPACITY. 

362. Use and Value of Storage. —Whenever the minimum rate of 
yield of a source of water-supply is less than the demand, the excess 
of demand over supply may often be furnished by storing up the sur¬ 
plus waters during periods of greater yields. In the case of surface- 
water supplies the yield is very variable, and a large amount of storage 
is needed to make available even 50 per cent of the total flow. On 
the other hand the minimum flow is relatively so small that a compara¬ 
tively small storage is sufficient to increase many times the capacity of 
the stream to deliver uniform quantities. 

The artificial storage of surface-water in large volumes is usually 
accomplished by constructing a dam across the valley in question, thus 
forming an impounding-reservoir. Frequently it will be impossible or 
uneconomical to store sufficient water in a single reservoir, in which 
case several may be constructed on the same or different watersheds, 
thus forming a system of reservoirs. Considerable quantities of water 
are also often stored in excavated reservoirs of such capacity that they 
may be called storage-reservoirs. They are similar in construction to 
the smaller service or distributing reservoirs and will be discussed in 
Chapter XXVII. They are seldom used for impounding the flow of 
small streams, but rather for purposes such as sedimentation, storage 
of river-water to avoid the necessity of pumping during the floods, 
storage of ground-water to allow of more uniform operation of wells,, 
etc.* 

Natural lakes or ponds can frequently be utilized as reservoirs. 
Their value for storage will depend upon the amount their surfaces can 
be varied in elevation, and not upon their total capacity. 

* It has been proposed to construct storage-reservoirs of this nature on the 
Thames watershed for the London water-supply, there being few or no good natural 
reservoir-sites. 

3ii 







312 


IMPO UNDING PE SEP VOIPS. 


363. Factors to be Considered. —In all questions of storage there are 
three general factors to be considered: (1) the yield of the source for 
successive intervals of time; (2) the demand for all purposes for like 
intervals of time; and (3) the storage necessary or available. The 
problem may be to determine the storage necessary with the first two 
factors given, or it may be to determine the maximum possible demand 
from a given watershed when the amount of storage is limited, or it 
may be to determine the supplying capacity of the watershed for 
various volumes of storage when comparing the cost of different sources 
of water-supply. 

The yield of the source of supply has been discussed in Chapter VI. 
The demand to be considered includes not only the consumption for 
the city in question, but also the loss of water by evaporation from 
water-surfaces not included in the estimate of the flow of the stream, 
such as that from the area of the reservoir itself, also loss from leakage 
and percolation, and often the necessary withdrawals to satisfy the 
demands of riparian owners below. The reservoir surface* may be 
taken at from 3 to 5 per cent of the total area, but if the assumed area 
is found later to be materially in error, the computations may be 
revised. The amount of leakage through the dam will usually be very 
small, but with certain forms of construction may be large. This 
question is further discussed in succeeding chapters. 

The ultimate loss by percolation will not be large unless the dam 
is underlain by a porous stratum which will lead the water away 
underneath. A careful geological examination of the impounding area 
and of the cross-section at the site of the dam will determine this point. 
If porous earth overlies impervious strata, the ground-water flow may 
be made use of to increase the capacity of the stream; and, further¬ 
more, as a reservoir fills, such porous material will become fully 
saturated and will act to increase the capacity of the given reservoir 
beyond its apparent capacity. As this increase due to ground-water 
is difficult to estimate, it should be considered as an additional safeguard 
and not relied upon except under very favorable circumstances. Cases 
have been cited where the capacity has thus been increased 20 to 30 
per cent. 

A fourth factor to be considered is that of the effect of storage upon 
the quality of the water; and it may be desirable for the sake of the 
improvement resulting from storage to make the capacity greater than 
that determined from considerations of quantity alone. 

364. Appropriation of Surface-waters. —The quantity of water neces¬ 
sary to satisfy the demands of the riparian owners below the reservoir 


capacity of reservoirs. 


313 


is often an exceedingly difficult matter to determine, and usually 
becomes a question for the courts to settle. Practice differs greatly in 
different States, and in many of the Western States the water belongs 
to the State to dispose of as it sees fit. It is often expedient to buy up 
all rights and to utilize whenever necessary the entire flow of a stream, 
or to fix by contract the amount which will be allowed to flow. When 
full water compensation is given the amount is determined on the 
general principle that only that portion of the flow can be abstracted 
that is not ordinarily used by the riparian owners for legitimate pur¬ 
poses, such as for water-power, domestic uses, etc. This would 
usually mean that during the dry months all of the natural flow must 
be allowed to pass, and during the remainder of the year a uniform 
quantity equal in value for the uses in question to the former flow of 
the stream. The amount in any case would thus depend much on 
local circumstances. Many court decisions in this country have 
awarded damages for diverting flood-waters that were entirely use¬ 
less to the riparian owners. In England a volume equal to one- 
third the total flow has often been adopted as compensation. In any 
case the most of the flood-flow would be available, and this usually 
amounts to considerably more than half the total flow. 

365. Computation of Storage. —The method of computation described 
below is essentially that of Rippl.* It consists in graphically repre¬ 
senting the net yield of the source in question during dry periods, and 
in obtaining from the resulting curve the solutions to the various forms 
of the problem which may be presented. 

The method is as follows: From the measured or estimated flow of 
the stream for each month during the period to be treated, subtract 
the monthly loss by evaporation from water-surfaces not included in 
the estimate, the monthly loss by leakage, and the monthly compen¬ 
sation as previously determined. The result will be the net yield for 
each month. Add together the yields from the beginning to each 
month in succession; then from these figures construct a curve OA, 
Fig. 66, in which the abscissa of any point is the total time from the 
beginning of the selected period, and the ordinate is the total net flow 
during the time represented by the abscissa. The inclination of the 
curve at any point is thus equal to the rate of the net flow, a minus 
inclination, as at B, representing a negative flow. Now in like manner 
plot a curve of consumption, OC , which may ordinarily be assumed as 
a straight line, as the variation month by month is a refinement hardly 
warranted by the accuracy of the other data. 


* Proc. Inst. C. E., i.xxi p. 270. 



3 [ 4 


IMPO UNDING-RESER V01RS. 


The ordinates between the lines OA and OC will now represent 
the total surplus from the beginning, and where the two lines con¬ 
verge, as at B and D, the yield is less than the demand, and con¬ 
versely. The greatest deficiency occurring during any dry period B 
is found by drawing EF parallel to OC and tangent to the curve; and 
the amount of it is given by the maximum ordinate IG drawn from EF to 



the curve. The deficiency for any other dry period is likewise found, 
and the maximum so found is the storage volume required to supply 
the demand OC. The time during which the reservoir would be drawn 
down below high-water line would be represented by the horizontal 
distance between E and the point of intersection F. In like manner 
the storage capacity for any other rate, 0C\ may be determined by 
measuring from the tangent EF '. 

If the tangent from any summit does not intersect the curve, it indi¬ 
cates that during the period investigated the supply is not equal to the 
demand; and to insure a full reservoir at the point F } for example, it 
is necessary for the parallel tangent drawn backwards from G to inter¬ 
sect the curve at some point H. In investigating various dry periods 
it is therefore necessary to begin the curve a year or two back of the 
dry years to insure the accumulation of surplus water. When actual 
stream measurements are to be had covering a series of years, it is best 
to consider the entire period. 

If the yield is to be limited by the time during which the reservoir 
is to be drawn below high-water line, the rate of supply and corre- 





CAPACITY OF RESERVOIRS. 


315 


sponding storage can be determined by finding by trial the line of 
lowest slope which shall be tangent at a summit, and whose horizontal 
projection equals the time specified. If the storage is fixed and it is 
desirable to know what amount of water the area will yield at a con¬ 
stant rate per month, the rate is found by 
drawing the lines EF from various summits, 
which shall have their maximum ordinates, 

GJ , equal to the given storage. The rate 
is given by the line of least slope. 

If the case is one where the consump¬ 
tion cannot be assumed as uniform, the line 
OC will be a curve, and the desired infor¬ 
mation can be more easily got by replotting the ordinates between the 
demand and supply curves—the accumulated surplus—from a hori¬ 
zontal axis, as in Fig. 67. Storage volumes, etc., are then found by 
drawing the tangent lines EF, etc., horizontally. 

366. Storage Calculation from the Sudbury River Records. —The 
results of calculations of storage volumes based on the records of the 
flow of the Sudbury River watershed are given in Table No. 58. The 
data are from a more extended table by Mr. FitzGerald.* The Sud¬ 
bury watershed has 3^ per cent of water-surface, and the observed flow 
is reduced to monthly flow from one square mile of land-surface by 
correcting for evaporation from the water-surface. Then from these 
figures, and the yield from one square mile of water-surface as given 
by the difference between rainfall and evaporation, calculations are 
made of the yield of one square mile having various percentages of 
water-surface. These results are then plotted and the storage volumes 
for various rates of consumption determined in a way similar to that 
explained in the preceding article. Mr. FitzGerald estimated the 
evaporation for each month throughout the entire period, but nearly 
the same results would be obtained by using the mean monthly 
evaporations as given on page 54. 

Table No. 17, page 80, gives the data of stream-flow covering the 
most important part of the record, and from these figures and the mean 
monthly evaporations the student should be able to obtain storage 
volumes closely agreeing with those of the table up to a daily draught 
of 600,000 to 800,000 gallons, depending upon the percentage of 
water-surface. Beyond this the draught is greater than the average 
flow for the five years given, and a longer period would need to be 
considered. 

* Trans. Am. Soc. C. E., 1892, xxvii. pp. 267 268. 








IMPO UNDING-KESER VO IRS. 


"> 


16 


TABLE NO. 58 . 


STORAGE CAPACITY REQUIRED FOR VARIOUS DAILY DRAFTS FROM ONE SQUARE MILE 
OF WATERSHED CONTAINING VARIOUS PERCENTAGES OF WATER-SURFACE BASED ON 
SUDBURY RIVER RECORDS. 



0 per cent. 

10 per cent. 

25 per cent. 

Constant 
Daily Draft. 

Storage 
Volume 
per Sq. Mile. 

Length of 
Time Reser¬ 
voir is Below 
High-water. 

Storage 
Volume 
per Sq. Mile. 

Length of 
Time Reser¬ 
voir is Below 
High-water. 

Storage 
Volume 
per Sq. Mile. 

Length of 
Time Reser¬ 
voir is Belotf 
High-water. 

Gallons. 

Gallons. 

Months. 

Gallons. 

Months. 

Gallons. 

Months. 

• 

100,000 

314,000 

4 

15,012,000 

6£ 

53 , 565,000 

7 s - 

150,000 

3,006,000 

3 ^ 

19,642,000 

Ih 

59,665,000 

4 

200,000 

8,797,000 

7 i 

25,742,000 

7 i 

65,765,000 

. 84 

250,000 

17,997,000 

Ih 

33 . 338,000 

8 * 

71,865,000 

8* 

300,000 

28,473,000 

8* 

43,437,000 

8* 

78,807,000 

8 4 

350,000 

39,173,000 

9^ 

54 , 137.000 

9 s 

87,957,000 

9 s 

400,000 

51,303,000 

9^ 

66,050,000 

io| 

99,089,000 

IO S 

450,000 

63. 553 ,ooo 

9* 

78,300,000 

io s 

127,412,000 

2li 

500,000 

75,803,000 

9s 

90,550,000 

io \ 

2l| 

156,362,000 

2ii 

550 000 

88,053,000 

9 i 

105,987,000 

185,312,000 

22-g- 

22^ 

600,000 

100,651,000 

io 4 

134 , 937.000 

2li 

214,262.000 

650,000 

114,451,000 

io| 

l63.8S7.OOO 

2l| 

250 , 744,000 

92 s 

700,000 

139,950,000 

21 £ 

192 837,000 

22| 

336 , 044,000 

io6| 

750,000 

168,900,000 

2I4 

221,787,000 

23 i 

421 . 344,000 

ii 5 s 

800,000 

199,106,000 

58 j 

8°i 

297,460,000 

92 i 

506,644,000 

I2 5 s 

850,000 

250,328,000 

380 , 557.000 

IQ 7 i 

591 , 944,000 

144 

<700,000 

334,078,000 

93 s 

465 , 857,000 

116^ 

677,244,000 

165*' 


* Estimated. 


This table of storage volumes is considered a safe one to use for 
streams in New England. A similar table can be constructed for any 
locality where accurate data are at hand, and in such form the informa¬ 
tion can readily be used in estimating yields and storage volumes for 
other areas in the vicinity and for various parts of the same watershed. 

As an example of the use of the table let it be required to determine 
the necessary storage-capacity to supply a constant daily draught of 
7 million gallons from a watershed of 12 square miles having io per 
cent of water-surface. The draught from one square mile will be equal 
to 583,000 gallons, and by interpolation the reservoir capacity is about 
125 million gallons per square mile, or a total capacity of 1500 million 
gallons. It will be below high water for a period of 1 year 91 
months. 

367. Capacity of a System of Reservoirs. —If there are several 

reservoirs on the same watershed, the supplying capacity of any com¬ 
bination may be found by the use of the methods just described. 
Beginning with the reservoir farthest up the valley, the net flow is 
determined and plotted, from which the maximum possible average 

























LOCATION AND CONSTRUCTION. 


317 


draught is found. Whenever the supply exceeds this draught with 
full reservoir the excess passes to the next reservoir below and adds 
to the supply from its own tributary area. Its supply curve can now 
be drawn and capacity determined, and so on. 

LOCATION AND CONSTRUCTION. 

368. Considerations Affecting Location —The proper location of an 
impounding-reservoir requires the consideration of many elements. 
In the first place the location determines the size of the tributary 
watershed, and, as the capacity is directly dependent upon the size 
of the watershed, different locations will call for different capacities 
to furnish like quantities of water. 

The location is also very largely determined by the distance of the 
reservoir from, and elevation above, the point of distribution. Long 
distances require heavy expenditures for conduits or pipe-lines, but 
these expenditures are relatively less the larger the quantity of water 
dealt with. For large cities it will therefore be practicable to go much 
farther for water than for small cities. Regarding the elevation of the 
reservoir it is very desirable that it shall be sufficient to enable all or a 
part of the consumers to be served by gravity alone, and it will be 
economy to spend a relatively large sum of money for conduits or 
otherwise to secure this advantage. The necessary elevation for this 
purpose depends upon the required pressure at and elevation of the 
various points of distribution, and the head lost in conducting thence 
the water. These features are discussed subsequently and as separate 
problems, but in the actual case they are all interdependent and must 
be considered together. Distant locations at high elevations will often 
need to be compared in economy with near locations requiring the use 
of pumps. 

The question of future extension is an important one, especially in 
large works, and the selection of a certain watershed for a supply may 
be determined not so much by the location of a single reservoir as by 
the existence of sites for several reservoirs in order that the capacity 
of the watershed may in time be developed to its fullest extent as the 
demand for water increases.* 

In questions pertaining to cost the economy of a reservoir alone is 


* For important examples see Report Mass. Board of Health upon a Metropolitan 
Water-supply, 1895 ; Wegmann, The Water-supply of New York, 1896 ; Report upon 
Future Extension of the Water-supply of Brooklyn, 1896 ; Freeman’s Report on 
New York’s Water-supply, 1900. 




3 l8 


IMPO UNDING-RESER VO IRS 


measured by the cost per million gallons stored, but a more significant 
quantity is the cost per million gallons of daily supplying capacity of 
reservoir and watershed; or in case the reservoir is one of a system, 
the cost per million gallons supplying capacity added by the reservoir 
in question. 

369. Topographic and Geologic Features .—The most favorable lo¬ 
cation for a reservoir as regards topography is a point where the valley 
forms a comparatively broad level area bounded by steep slopes at the 
sides, and below which the hills approach close together so as to form 
a good site for a dam. Such an ideal site is rarely found, and it will, 
usually be necessary to compare two or more possible sites, for which 
purpose careful estimates of cost will be required. A site which will 
include much swampy area or involve a large amount of shallow 
flowage is objectionable on the grounds of quality. 

To prevent the escape of water the floor of the reservoir should 
contain no outcrop of porous strata of any extent which may lead the- 
water away underground, and in the vicinity of the dam or embank¬ 
ment it should be underlain by an impervious stratum at a depth that 
can be reached by that structure. In some cases these conditions 
cannot be secured and some loss through porous ground must be 
expected. 

Besides the character of the substrata in the vicinity of the dam, 
the kind of soil, proximity of suitable stone for a masonry dam or of 
material for an earth embankment, are questions controlling to a large 
extent the location of a reservoir. 

370. Surveys and Preliminary Work. —To make even a preliminary 
determination of reservoir-site in accordance with the preceding^ 
principles requires a fairly accurate knowledge of the areas of various 
portions of the watersheds and of their relative elevations. If this 
information cannot be obtained from existing maps, a reconnoissance 
survey must be made. For this purpose the transit and stadia method 
is well adapted. 

After a tentative location has been decided upon, accurate levels 
must be run to connect the town with the reservoir-site, also surveys 
for conduit lines, and an accurate topographical survey of the area to 
be flooded and all that may be affected by the reservoir. This survey 
should include information as to all buildings upon and adjacent to the 
area in question, nature of the vegetation, location of roads, property 
lines, etc. In addition to this it will prove of much subsequent value 
to have a topographical survey made of the entire watershed, which 
may be less accurate than that for the reservoir. At the same time a. 


LOCATION AND CONSTRUCTION . 


319 


complete sanitary survey of the watershed can be made, as outlined in 
Chapter VIII, page 137, and a good topographical map will prove of 
great convenience in this connection. 

Determinations should be made of the character of the soil, amount 
of organic matter at various depths, especially in swamps or old ponds, 
and nature of substrata with reference to its permeability. At the site 
proposed for the dam numerous borings must be made extending to a 
considerable distance above and below the dam as well as on the 
flanks, and these must be supplemented by test-pits so that the nature 
of the supposed firm stratum can be accurately determined. If a suitable 
foundation cannot be reached at a reasonable cost, the site may have 
to be abandoned. 

371. Depth of Reservoir. —Calculations of storage volumes for differ¬ 
ent depths can readily be made from the contour map. The areas 
enclosed by each contour can be measured by a planimeter and the 
volume between any two successive contours taken as equal to the 
average of the areas enclosed by the contours, multiplied by the con¬ 
tour interval. Where the slopes are very flat this method gives an 
appreciable error, and in that case it may be advisable to employ the 
prismoidal formula. By this formula, the volume of two successive slices 
in terms of the three areas a, b, and c (the two end and the intermediate 

d 

areas) is equal to (a -f- 4b + c)—, where d is the contour interval. The 

volume up to any given contour having been determined, the necessary 
height of dam to hold any given quantity of water becomes known. 

From considerations of quality, it should never become necessary 
to withdraw the water to the very bottom of a reservoir, so that the 
volume for a few feet in depth at the bottom should be omitted from 

the calculations. What this depth should be depends upon the char- 

/ 

acter of the water and the shape of the basin. It may be taken, with 
very little loss of capacity, at one-fifth or even one-fourth the total 
height of the dam. With sediment-bearing streams some allowance 
should be made for the silting up of the reservoir, the amount of which 
can be estimated from analyses of the water. In the case of some 
streams this is a matter of importance and may involve considerable 
expense for the removal of the sediment from time to time. 

A noteworthy case of the rapid silting up of a reservoir is that of 
the reservoir formed by the dam across the Colorado River at Austin, 
Texas. This dam was completed in 1893, and at that time formed a 
reservoir of a capacity of 17,000 million gallons, whereas in February, 
1900, the capacity had become reduced to 8600 million, or only 52 per 


320 


IMPO UNDING-RESER VO IRS. 


cent of the original amount. The cause of this large amount of deposit 
was the very large discharge of a silt-bearing stream as compared to 
the capacity of the reservoir.* 

Where the volume is not fixed, as in the case of a series of reser¬ 
voirs, the economical height is determined by comparative estimates of 
cost for various volumes. Such estimates must of course include 
expense for land, water rights, etc., as well as for the constructive 
features. 

372. Cleaning the Site. —In Chapter IX the injurious effect upon the 
quality of the water of organic matter in reservoirs was discussed, and 
the necessity for the removal of all vegetation and perishable matter 
from the reservoir-site was pointed out. Still further it has been shown 
to be desirable and of great benefit to the water to remove the top soil 
to a sufficient depth to include most of the organic matter therein. 
Such stripping has for some years been done for some of the large 
reservoirs of the Boston Water-works and at other places, especially in 
Massachusetts, with the result that the impounded water from the first 
has suffered no deterioration by storage. In other reservoirs where 
this has not been done, trouble has been experienced for many years. 
Where the deposit of organic matter is very deep, and the expense 
of removing too great, a covering of gravel is advisable. 

In investigating the soil from the site of the proposed Nashua 
reservoir, Dr. T. M. Drown of the Mass. Board of Health found that 
the amount of organic matter in a soil decreases rapidly with the depth. 
The percentage at the surface was usually 8 per cent or more, while 
at 10 or 12 inches below there was usually but 1^ to 2 per cent. As 
a result of this study he suggests these lower figures as a provisional 
standard for the permissible percentage of organic matter which may 
be allowed to remain. + 

As an example of soil-stripping on a large scale mention may be 
made of the work done on Reservoir No. 5 of the Boston Water-works.^: 
The soil was in general removed to a depth of about 1 foot, but in 
places to a much greater depth. In one pocket of mud 20 feet deep 
the amount of organic matter at the surface was 75 per cent, and at 10 
feet deep, the depth of the excavation, it was 5 per cent. The total 
amount removed in this way was about 4 million cubic yards, adding 
in this way about 10 per cent to the capacity of the reservoir. In the 
proposed Nashua reservoir the cost of such removal is estimated at 
nearly $3,000,000. 

* Eng. News, 1900, xliii. p. 135. 

f Report Mass. Board of Health, 1893, p. 383. 

\ Eng. News, 1897. XXVII. p. 130. 




MAINTENANCE OF RESERVOIRS. 


321 


373. Shallow Flowage. —As a further protection to the quality of 
stored water it is desirable that there be as little area alternately 
flooded and exposed as possible, in order to limit the growth of vege¬ 
tation. Here again the practice of the Boston Water Board is to be 
recommended. The minimum depth at high water allowed in Reser¬ 
voir No. 5 is 8 feet. Shallow places are either excavated to this depth 
below high-water line, or are partly excavated and partly filled, the 
slopes being formed at 3 to 1 and covered with 2 feet of gravel. 

374. Maintenance.—111 maintaining a reservoir so as to preserve the 
quality of the water and to supply the necessary quantity regularly and 
certainly requires a considerable degree of care and attention. To 
keep the quality as good as possible requires first of all that the water¬ 
shed and reservoir be kept free from organic pollution. To insure that 
this is the case the city should have sanitary supervision over the area 
in question, and inspection should be regularly made to see that all 
sanitary requirements are complied with.* 

In addition to the prevention of pollution from animal sources it is 
desirable that the reservoir be kept as free as possible from vegetation. 
During seasons of low water, opportunity is offered for removing the 
vegetation from around the borders of the reservoir. Where there is 
more or less unavoidable organic matter present in the water there will 
at times be objectionable tastes and odors at certain depths. To 
obtain the best water available the depth at which it is drawn from the 
reservoir should be varied from time to time according to the condition 
of the water. Frequent analyses of water drawn from different depths 
are very valuable in this connection. 

When reservoirs have become silted up to a considerable extent it 
may be necessary to remove the deposit. If the dam be located in a 
narrow valley, much can be removed by flushing through sluice-gates. 
The greater part of the material will, however, have to be taken out by 
methods similar to those used in ordinary excavations. In case the 
silt brought down contains much organic matter it should be removed 
frequently in order to prevent trouble from its decay. 

Careful records should be kept at the reservoir of all matters which 
may be of any value in subsequent designs for enlargement or for new 
works. These should include records of rainfall, temperature, height 
of water in reservoir, amount passing over waste-weir, and data per¬ 
taining to the quality of the water at different seasons of the year. 

The maintenance of dams and embankments should call for very 

* For details of methods of making such inspection and the requirements which 
have been imposed in certain instances see Reports N. Y. State Board of Health, 
1889, 1R94. See also Literature of Chap. VIII. 




322 


1MP0 UND1NG-RESER VGIRS. 


little labor. Earthen embankments should be kept neat in appearance 
with slopes well sodded, or covered with large gravel so as to be per¬ 
manent. The top of the embankment should of course be maintained 
at its full height, and the waste-weir and the channel below it kept 
clear and of the designed capacity at all times. Gates and other 
apparatus should be frequently inspected and kept in thorough repair. 
Flashboards should be used with great caution, if at all. They should 
always be so designed that they will fall or be washed away when the 
water begins to flow over them. Immediate attention should be given 
to any sign of increased leakage in the case of either an earthen or a 
masonry dam. Leaks or excessive seepage in masonry dams may be 
often stopped by plastering the up-stream face of the dam with rich 
cement mortar. Any visible cracks may also be filled with Portland- 
cement grout forced in under pressure. Earthen dams are repaired 
with difficulty. If the seepage-water flows perfectly clear, the indica¬ 
tions are that no material is being carried away and that there is no' 
immediate danger of the leak enlarging. If the seepage-water, on the 
other hand, be muddy and continue so, the water should be drawn off 
at once and the dam repaired. This may sometimes be accomplished 
by excavating to a moderate depth at the upper end of the leak and 
filling with puddle well rammed into place. If the leak is a serious 
one, it will probably be necessary to cut down from the top and fill with 
good material well bonded into the old part of the work, and compacted 
in the same manner as for a new embankment. 

LITERATURE. 

1. Rippl. The Capacity of Storage-reservoirs for Water-supply. Proc. Inst. 

C. E., 1882-83, lxxi. p. 270. 

2. Stearns. The Selection of Sources of Water-supply. Jour. Assn. Eng. 

Soc., 1891, x. p. 485. 

3. FitzGerald Rainfall, Flow of Streams, and Storage. Trans. Am. Soc. 

C. E., 1892, xxvii. p. 304. 

4. Drown. On the Amount and Character of Organic Matter in Soils and its 

Bearing on the Storage of Water in Reservoirs. Mass. Bd. Health 
Report, 1893, p. 383. 

5. Hooker. Storage-capacity in Lakes and Reservoirs. Eng. Record , 1894, 

xxix. p. 205. 

6. Frizell. Storage and Pondage of Water. Trans. Am. Soc. C. E., 1894, 

xxxi. p. 29. 

7. Greenleaf. A Method for Determining the Supply from a Given Water¬ 

shed. Eng. News, 1895, xxxiii. p. 238. 

8 . Horton. A Form of Mass Diagram for Studying the Yield of Watersheds. 

Eng.Record, 1897, xxxvi. p. 285. 

9. Taylor. The Silting up of Lake McDonald and the Leak at the Austin 

Dam. Eng. News, 1900, xliii. p. 135. 


CHAPTER XVI. 


EARTHEN DAMS. 

GENERAL CONSIDERATIONS. 

375. The Requisites of a Dam. —The function of a dam is to prevent 
the passage of water. To this end it must be impervious, or sufficiently 
so to prevent excessive loss of water; and it must be stable. The 
possible consequences of a defect in the latter requirement are exceed¬ 
ingly serious, as has been demonstrated by the great loss of life and 
property caused by the failure of reservoir embankments in the past. 

These two properties, imperviousness and stability, may or may 
not be independent of each other, according to the nature of the con¬ 
struction ; but it will in any case be of advantage to consider them as 
distinct and separate. In other words, a dam must have an impervious 
body, and this must be safely supported. 

376. Kinds of Dams.— Dams may be divided according to the 
material used into five classes: earthen dams, masonry dams, loose-rock 
dams, wooden dams, and iron or steel dams. These materials are also 
used in various combinations. The form of dam suitable for a given 
case depends upon the character of the foundation, the topography of 
the site, the size and importance of the structure, the degree of imper¬ 
viousness required, and the cost. Of the above kinds of dams those 
of masonry and of earth are the ones usually considered and will here 
be fully treated. The other forms will be treated as fully as their 
importance seems to warrant. 

377. The Dam as a Porous Structure. —Before proceeding with the 
discussion of the various forms it will be well to consider the action of 
the dam as a porous structure. Few dams are absolutely impervious 
and many are far from it, yet they may do good duty as impounders of 
water; but whether a dam is impervious or not is a matter that in most 
cases greatly affects the stability and should be carefully considered. 

Let ABC , Fig. 68, be a body of porous material (whether very 

323 


324 


EARTHEN DAMS. 


porous, as sand or loose rock, or only slightly so, as most masonry 
dams, is for the present immaterial), resting upon a porous foundation 
and retaining water at the level D. Under the assumed conditions 

some water will percolate through 
and under the dam and escape at C 
in a way similar to the flow of 
ground-water. The surface of the 
percolating water will be some 
FlG ‘ 68 ‘ curve, such as DEC , the slope of 

which at any point measures the relative resistance to flow. The 
amount of water percolating varies of course with the porosity, but 
even with fine sand or earth it will be very small, so that the require¬ 
ment as to imperviousness may be met with a porous material. 

A dam to be stable must be able to resist being pushed or slid along 
Dy the water, it must not be overturned, and it must not be ruptured 
or overstrained in any of its parts. The first two conditions are 
dependent upon the weight of the structure, and it is important to 
inquire what effect the percolation of water will have upon this factor. 

378 - The Buoyant Effect of Percolating Water. — If the material 
consists of loose grains like sand or earth, the loss of weight for the 
portion submerged is equal to the weight of the water displaced. If p 
is the ratio of porosity by volume, the volume of water displaced for 
each cubic foot of the material is 1 — the weight of which is. 
(1 — /)62-5 pounds. Thus with a porosity of 40 per cent the loss in 
weight of sand, weighing, say, 100 pounds, will be (1 — .40)62.5 = 37 
pounds per cubic foot, leaving a net weight of 63 pounds. 

If the material is cohesive like stone or cement, the water cannot 
exert an upward pressure upon the entire surface of any horizontal sec¬ 
tion, and the buoyant effect will be much less than the above. Assum¬ 
ing that the full effect will occur whenever the porosity is as great as 
33I per cent (this being approximately the porosity of well-compacted 
sand), and that with a cohesive material of less porosity it will be pro¬ 
portional to the porosity, the buoyant effect in such cases will be 

P 

— ( r — /)62.5 = 3/(1 — p)6 2.5 pounds per cubic foot; and the upward 

s 

pressure on any vertical column of masonry of 1 square foot in cross- 
section will be equal to 3/(1 — p)62. 5 X h , where h — distance of the 
base of this column below the surface curve DEC (Fig. 68). Thus in 
a homogeneous masonry dam having a porosity of 5 per cent, the 
buoyant effect on the submerged portion will be approximately 
3 x -05(1 — .05)62.5 = 9 pounds per cubic foot. That hydrostatic 










GENERAL CONSIDERATIONS. 


325, 

pressure maybe readily transmitted through porous stone has been fully 
shown by experiments and would in any case hardly admit of doubt.* 

In a structure of stone having a small porosity /, with mortar joints 
of large porosity p' , the buoyant effect at the joints will be great and will 
be equal to 3/ (1 — p )6 2.5 X h. If any loose joint exists, or any place 
where the water can enter in “ thin sheets,” then p' becomes the same 
as assumed for loose material, namely, 33-J per cent, and the buoyant 
effect is again equal to (1 — p)62.$ X h, as for sand. To reduce this 
effect as far as possible in masonry it is thus seen to be necessary to 
make the joints of as little porosity as the stone itself. If the founda¬ 
tion be more porous than the masonry, and open to the percolation of 
water, the maximum buoyant effect will be at the bottom and measured 
by the porosity of the foundation. 

379. Form of the Curve of Pressure .—Since the weight and stability 
of a dam are decreased by percolating water, and the decrease is 
measured by the head h at any point, or the distance of the point below 
the curve DEC (Fig. 68), it is evidently of advantage to either prevent 
percolation entirely or to lower this curve as much as practicable. 
Now the slope of this curve measures the relative resistance to flow, so 
that if this resistance is made relatively great near.the upper side, the 
line will take some form, DE'C, thus increasing the effective weight of 
the material. This result is obtained in various ways, as, for example, 
in earthen embankments by the use of more impervious material on the 
up-stream side, and in masonry dams by plastering the upper side or 
by drainage of the lower side, etc. It will be noted that with a porous 
foundation attention must be paid to the flow of water underneath the 
dam as well as through it. 

THE EARTHEN EMBANKMENT. 

380. Advantages and Requisite Conditions. —The earthen embank¬ 
ment is the most common form of dam. It can be built on a variety 
of foundations; it is commonly the cheapest form, and when well 
designed and executed is an entirely safe and reliable structure. The 
stability of an earthen dam is, however, so closely dependent upon its 
imperviousness that, compared to some other forms of dams in which 
these functions are more independent, the necessity for making the 
dam impervious is relatively great. The properties of the materials 
used are also less uniform and less well known than those of other 


* See paper by Ross and Broenniman on the Hydrostatic Pressure in Masonry, 
Jour. JVsst. Soc. Engrs ., 1897, II. p. 449 - 





.326 


EARTHEN DAMS. 


materials, such as stone and timber, so that a very large margin of 
safety must be used. 

Where flood-waters have to be passed over a dam some other 
material than earth must be used for at least the portion of the structure 
subjected to water action. Water flowing over an earthen embank¬ 
ment is inadmissible, many failures having been caused by such occur¬ 
rence, due to faulty construction. For dams higher than ioo feet or 
thereabouts few engineers would recommend an earthen structure. If 
the foundations are suitable, a masonry dam is in such cases greatly 
to be preferred. It is more reliable, and with the great pressures 
occurring it is desirable to have all outlet arrangements built in 
masonry. Several recent high dams have been constructed partly of 
-earth and partly of masonry, the higher central portions being of the 
latter material. 

381. The general requirements of a good foundation for an earthen 
dam are that an impervious stratum can be reached at a moderate 
depth, and that the material near the surface is sufficiently compact 
to support the load. A compact clay or hardpan makes the best 
foundation. Solid rock is also good if not fissured. Mere porosity 
is comparatively unobjectionable, but a rock through which water is 
liable to pass in cracks and fissures makes a very bad foundation for an 
earthen dam. Embankments of earth have been successfully con¬ 
structed on foundations of sand; but in such a case it is important that 
the sand be fine and of a uniform character, containing no streaks of 
coarse material which will offer little resistance to the flow of water. 
Soft foundations have also been built upon in cases of necessity, but 
both porous and soft materials should be avoided if possible. 

382. Forms of Construction. —Earthen dams are of a trapezoidal 
form with top width, side slopes, etc., proportioned according to the 
material used. Several types of embankments are employed, the one 
used in any case depending upon the material at hand and upon the 
individual preference of the engineer. 

1. The Homogeneous Embankment. —Where good material is at 
hand in sufficient quantities the entire embankment may be made of 
uniform consistency and all as nearly water-tight as possible. Usually, 
however, it will be more economical and give as good results to put 
the best material near the upper side of the embankment, changing 
gradually to the more porous material towards the lower face. 

2. Embankments with Core-walls .—Where good material is scarce, 
imperviousness is usually obtained by means of a wall of impervious 
earth or masonry placed near the centre of the dam. If imper- 


FORMS OF CONSTRUCTION. 327 

vious foundation is reached only at a considerable depth, this portion 
only of the embankment is carried to the extreme depth. 

3. Porous Embankments or Embankments on Porous Foundations 
are sometimes necessary from lack of suitable material; they require 
special precautions to insure their stability. 

383. Stability of the Various Forms of Embankments. —The chief 
danger of failure of an earthen embankment lies in its destruction 
through percolation or in being overtopped by floods. It is, however, 
desirable to consider also the stability against sliding on the base, and 
in some localities it is necessary to make the design with reference to 
the possibility of overloading the foundation stratum. The matter of 
soft foundations will be treated later, but the questions of impervious¬ 
ness and frictional stability will be considered here. 

The conditions would rarely be such as to make it likely that a dam 
could fail by actually sliding as a whole on its base. Lack of stability 
to resist water-pressure would be shown rather by slips of portions of 
the embankment at the outer slope. The stability in this respect is, 
however, approximately indicated by the frictional stability at the base 
and at other horizontal sections. 

384. The Embankment Without Core-wall. —In case the embank¬ 
ment is impervious, either when made entirely of impervious material 
or when only the upper portion is so made, the internal water-pressure 
is zero, as it is assumed that no water 
percolates. The forces acting will 
then be as shown in Fig. 69. The 
force tending to cause sliding along the 
base is P sin a, and the maximum 
resistance would be Vc, where c — 
coefficient of friction of the material. Here V is large, being equal to 
W -\- P cos a, hence the factor of safety against sliding is in this form 

Vc 

relatively large and equal to p ~^—• If imperviousness is not per¬ 
fectly secured in a homogeneous dam, water-pressure will exist within 
it which will reduce the effective weight of the material, as explained 
in Art. 378. It was also there shown that to avoid this as much as 
possible the upper portion should be more impervious than the lower 
portion. In this way great stability can be secured with porous 
materials. 

385. The Embankment with Core-wall. —In this form reliance is 
chiefly placed on the core for imperviousness. If it is placed at the 
centre, as in Fig. 70, and is more impervious than the material above it, 







328 


EARTHEN HAMS. ‘ 


the line of pressure, AB, on the up-stream side must be assumed nearly 
horizontal. If the material below the core be relatively porous, as it 
should be, then there will be no water in the lower portion of the dam. 
The water-pressure will then be applied practically horizontally on the 
core-wall, and dependence for stability against sliding must be placed on 
the wall and material below. In Fig. y i is shown the part of the 
embankment below the upper face of the core-wall. Let h — depth 
of water; bh — width of this portion of the dam at water-level; ^ = 
slope of outside face in terms of ratio of horizontal to vertical projection ; 
w — weight of a unit volume of water; w' — weight of a unit volume 




of dry embankment material; and W = weight of a slice of embank-* 

zuJft 

ment one unit long. The pressure of the water will be P — ——. The 

weight of embankment = W = w'h[bk -f- If c = coefficient of 

Friction, the factor of safety against sliding is 


w'hibh 4- —V 
V 1 2 / w’ 

wh 2 = w X c ( s + 2 ^' 

* 2 


If the slope s is made as steep as the material will stand, then 
c = — and the factor of safety becomes equal to 



(i —J - 2 be ). 


If w f = ioo pounds per cubic foot, and w = 62.5 pounds, then to 

I 2 t 

secure a factor of two would require b to be equal to ’—If c 

c 

= 2:1), this would give a value of b equal to .25; that is, the 






















MATERIAL FOR EMBANKMENTS. 


329 


width at the water-line must equal .25 h. Usually the width is greater 
than this. To further increase the stability the outside slope should 

be made greater than —. It should thus be made about 2 to 1 if the 

material will just stand at 1 ^ to 1 (c = -f). With s = 2 and c — -J, a 
factor of safety of 2 would be secured with b — o. 

In this discussion the possible pressure of water-soaked material 
upon the core-wall has been neglected. What this would be is 
impossible to say, but before sliding could take place it would also 
have a downward component against the wall, thus adding to the fric¬ 
tion. The above analysis is, however, sufficient to show the desira¬ 
bility of rather flat slopes on the down-stream side, a considerable 
width at the water-line, and, in order to secure the full benefit of 
weight, the lower half of the embankment should be relatively porous 
and heavy. It is also plain that the weakest section is at the bottom. 

386. Material for Embankments. —Various kinds of material can be 
used to make an embankment. Loam, sand, gravel, and clay, mixed 
in various proportions, are common. For the first three to be imper¬ 
vious they must contain a certain proportion of clay, the amount 
required depending upon the variation in size of the coarser particles. 
The suitability of a material for embankment construction can to some 
extent be determined by experiments. It should be strongly cohesive 
and plastic when mixed with water, and should be impervious; but the 
correct valuation of natural mixtures requires much experience in their 
actual use in construction. If sufficient impervious material is not 
available to form the entire embankment, the best is to be selected for 
this purpose and confined to the upper portion or to a puddle core. 
For the lower portion, coarse heavy material is suitable. 

Considerable difference of opinion exists among engineers as to the 
best material for embankments or core-walls. English practice favors 
a puddle of clay with little or no gravel, while most American engineers 
favor a gravel and clay puddle. Impervious cores or embankments 
can be made of either material, and where fully protected from wash, 
and from becoming dried out, are equally satisfactory. Clay shrinks 
greatly in drying, thus forming cracks, and a pure clay will shrink much 
more than a mixture containing only 15 or 20 per cent of clay, an 
advantage in favor of the mixed material. The latter is also much the 
safer against wash in case of leaks, and is more suitable for the main 
body of the embankment and for use in exposed situations. It is also 
less easily attacked by woodchucks, muskrats, etc. Clay dissolves 
and washes away very easily on account of the minute size of the 


EARTHEN DAMS. 


33C 

particles. It is therefore very essential to the stability of a clay wall 
that there be no percolation through it. For confined locations and 
in thin sections, a clay containing only coarse sharp sand is probably 
better than one with gravel. 

If good material does not exist already mixed, artificial mixtures 
of gravel, sand, and clay may be used. A fairly uniform sand or 
gravel contains about 40 per cent of porous space. If then a mixture 
be made of coarse gravel, fine gravel, and sand, in each case just 
enough of the finer material being used to fill the interstices of the next 
coarser, there will be in the mixture a porous space equal to .40 X - 4 ° 
X .40 = 6.4 per cent, which will represent the proportion of clay 
necessary to make the mixture impervious. In practice it will take 
considerably more to insure the filling of all the interstices, as much 
as 1 5 or 20 per cent, depending upon the nature of the gravel mixture. 
In any case the percentage of voids in an artificial mixture can be 
readily determined by tests with water. 

Porous embankments may be formed of sand, gravel, or loam, and 
if properly constructed are in some respects safer structures than one 
made largely of clay. If the material is properly graded from fine to 
coarse from the upper side to the lower, the fine material will act to 
prevent water coming through with sufficient velocity to wash away 
the coarser particles below which furnish stability to the structure. 

387. Core-walls.— Pjiddle Cores. —Much has been written regarding 
the use or omission of core-walls, and the material of which they should 
be made. Theoretically, core-walls are needed only when the body 
of the embankment cannot readily be made water-tight. With an 
abundance of good material there is no object in using a core-wall of 
earth except perhaps that the chances of getting good work done are 
better if attention is concentrated on a small section. With a smaller 
quantity of good material it is best to concentrate it in a body, and 
with material still more scarce it will naturally be placed in a wall or 
puddle core. As between a bank in which the clay is confined to a 
narrow wall, and one where the same amount is mixed with a suitable 
proportion of gravel and forms a larger part of the embankment, the latter 
will be preferable. In deep trenches, and especially where much water 
is met with, a concrete filling is frequently used for a part of the depth. 

For a puddle wall the minimum thickness ordinarily used is 4 to 8 
feet at the top and about one-third the depth of water at the bottom, 
with a uniform batter on both faces. The trench is also usually made 
with a batter, the width at the bottom being one-third to one-half that 
at the ground-level, with a minimum of 4 or 5 feet. 


CORE- WALLS. 


33 * 


388. In Fig - . 72 is illustrated the embankment of a distributing 
reservoir at Syracuse, N. Y., built with a low core-wall. The material 
composing the body of the embankment was a mixture of heavy clay 
and a small amount of gravel. All hard lumps were broken up and all 
stones more than 4 inches in diameter were removed. The trench was 



about 8 feet deep and 12 feet wide, and was filled with clay in 4-inch 
courses puddled in place.* 

An embankment with full puddle core and selected material 
adjacent is shown in Fig. 73, which is a section of a reservoir embank- 



Fig. 73. —Section of Reservoir Embankment, Glasgow Water-works. 


ment at Glasgow, Scotland. + The foundation stratum was of exceed¬ 
ingly varying nature, and at one place the trench was carried to a depth 
of 195 feet. 

389. Masonry Core-walls .—Instead of a core of puddle, many 
engineers prefer a core of rubble masonry or of concrete, made as 
impervious as possible. The advantages of this over a core of puddle 
are its safety against attack by burrowing animals, safety against wash 
in case minute leaks occur, and the greater certainty with which a con¬ 
crete wall can be made impervious, especially where it joins the foun¬ 
dation. It is also much better suited for placing in wet trenches, and, 
its thickness being less, the trench need not be as wide. Furthermore, 


* Trans. Am. Soc. C. E., 1895, xxxiv. p. 37. 
\ Engineering , 1894, lvii. p. 704. 















































332 


EARTHEN DAMS 


in case of an overflow the failure of the dam will be much delayed by 
a wall of masonry. The chief objections raised against it are its 
greater cost and the fact that with it the bank is less homogeneous and 
hence more difficult to construct, and more subject to injury by unequal 
settlement. Core-walls if made too thin are also liable to rupture from 
unequal earth-pressures. For these reasons it is even more important 
to avoid much settlement by a very careful compacting of the material 
than in the case where the embankments are entirely of earth. 

On the whole, the practice in the eastern part of the country 
strongly favors masonry core-walls, especially for high embankments, 
and many engineers would use them as an extra precaution even where 
the entire embankment is of good material. In the West they are 
seldom used, and some of the highest embankments have been con¬ 
structed without them. 

Core-walls should be made with a batter, as this tends to prevent 
the separation of earth and masonry from settlement. Short buttresses 
constructed at intervals on the up-stream side are an additional precau¬ 
tion against the passage of water along the face of the core-wall. 

To secure imperviousness the concrete should be relatively rich in 
mortar, and it is also advisable to plaster the upper face with neat 
Portland-cement mortar. This is the practice of the Boston Water 
Board, and in dams so constructed experiments show that the full 
water-pressure is resisted at this point. 

Masonry core-walls are made of various widths. Sometimes in 
case of embankments made of good material, they are made only a foot 



Fig. 74. —Section of Dam No. 5, Boston Water-works. 

or two thick, their purpose being mainly to prevent the passage of 
burrowing animals. Ordinarily, however, a core-wall is made 2 to 4 
feet thick at the top, with a batter of £ to f inch per foot on each side 
down to the trench and then with vertical faces below. The height of 
a core-wall should be equal to that of the highest water-level. 

390. Fig. 74 is a section of the earthen portion of Dam No. 5 of the 
Boston Water-works, and represents what may be considered as the 














COKE-WALLS. 


333 


most advanced practice in this type of construction.* Fig. 75 is the 
section, as designed, of the earthen portion of the New Croton Dam. 
The masonry core extends to solid rock. The dam as constructed is 
not so high above foundation as the section shown. + 

391. Core-zvalls of Wood and Steel. —Sheet-piling is sometimes 
used to good advantage in the bottom part of an embankment, but to be 
durable it must be in a position where it will be kept constantly wet. 
It is especially serviceable with low embankments built on a porous 
foundation and in temporary work. 

A core of steel imbedded in concrete has been used in a rock-fill 
dam at Otay, Cal. The steel varied in thickness from No. o to No. 3, 
Birmingham gauge (.34 inch to .259 inch). The plates were riveted 
and calked and coated with asphalt. This steel core was protected 



on each side by a wall of concrete 1 foot thick. (See Art. 457-) 
Such a wall in an earthen embankment would be absolutely safe against 
percolation even though slight cracks should form in the masonry. 
Compared to a wall entirely of masonry it could be made much thinner 
for the same strength, and as the cost of a J-inch plate would not be 
more than the cost of 1 or 2 feet of concrete, a considerable saving 
•could be effected. At the bottom and ends of the dam the masonry 
wall should spread out to the ordinary width. In a thick core-wall 
the riveting and calking of the plates might be dispensed with. 

392. Position of Core-zvalls. — In embankments for impounding- 
reservoirs core-walls are usually placed at or near the centre of the 
dam. The effective weight of the structure would evidently be 
increased by placing it near the up-stream face, and this is sometimes 


* Eng. News , 1895, xxxm. p. 230. 
f Proc. Am. Soc. C. E., Jan. 1900, p. 2. 

















334 


EARTHEN DAMS. 


done where made of puddle. The disadvantages of so doing are that 
much more puddle is required for the same thickness, it is not so readily 
placed, and is more exposed to frost and water action and to drying 
out when the water is low. There is also more danger of slips when 
the water is drawn down, such as have occurred in several places. 

393. Embankment Slopes.—Much variation exists in practice in the 
matter of side slopes, even with similar material. On the water side 
the slope is usually protected from wave action and should only be 
sufficient to prevent slips. With coarse material this need not be flatter 
than 2 horizontal to 1 vertical. With finer material it may need to be* 
2 2 or 3 to 1, or in some cases even 4 to I, since earth in a saturated 
condition has a comparatively small angle of repose. On the lower 
side the material will be dry if made more porous than the upper por¬ 
tion, and the angle of repose will be about ij to 1, but the stability of 
the embankment is largely dependent upon the lower half, as pointed 
out in Art. 385, and it is desirable to use a somewhat flatter slope than 
that at which the material will just stand. A slope of 2 to 1 is there¬ 
fore to be recommended, although 1J to 1 has frequently been used. 
If the material will stand at 1 to 1, as broken stone, for example, then 
a slope of i j to 1 would be suitable. On high embankments, bermes 
placed 30 to 40 feet apart vertically are a desirable feature. On the 
up-stream side they form additional supports for the paving, while on 
the down-stream side they allow of lateral drainage by means of paved 
gutters, thus protecting the slope to a considerable extent from scour 
due to heavy rains. This arrangement also gives a little greater safety 
and stability at the bottom of the embankment where it is the weakest. 
Below the berme the slope is often made flatter than above, thus secur¬ 
ing some additional width with little extra cost. This modified form is 
particularly adapted to soft foundations. 

394. Height above Water-line. —The top of the dam should extend 
sufficiently above the high-water line to protect the material exposed 
to water action from frost and to give a safe margin against overflow¬ 
ing. This will be equal to the depth reached by frost plus an allow T - 
ance of 2 to 5 feet for wave action, depending on the exposure to winds 
and the depth of the water. A formula given by Stephenson for height 
of waves in such cases is 

h — i.5vz>+ (2.5 — rzj), 

in which H — height in feet and D — length of exposure, or “fetch,” 
in miles. For very low embankments the height as determined above 


EM BA NKMEN T SL OPES. 


335 


is not always attained, more dependence being placed upon width of 
top, which will be relatively great in such cases. In climates where 
protection from frost is not required there should be a larger margin of 
safety between the highest waves and the top of the dam, as an earthen 
embankment must not be overtopped by the water. 

395. The Width of Top is frequently fixed by requirements for a 
roadway. Where not so fixed it is made to vary with the height, — 
from 6 to 8 feet for very low embankments to 20 or 25 feet for embank¬ 
ments 80 to 100 feet high, or, approximately, width h -J- 5 feet, 
where h — height of dam. 

The reasons for increasing the width with the height of embank¬ 
ment are to secure safety against the increased action of waves and of 
ice, and to add to the general stability of the structure. With no 
increase in top width a high embankment would be relatively less 
secure than a low one, while it is desirable to have it the reverse on 
account of the much more serious results of a failure of a high embank¬ 
ment. 

396. Preparing the Foundation. —In preparing the foundation the 
surface-soil must be removed over the entire site of the embankment 
to a depth sufficient to reach good sound material. All roots, stumps, 
and other perishable material must be removed, as any such material 
by decaying offers a passage for water. For high and heavy embank¬ 
ments it is important that the excavation under the main body of the 
dam, and especially near the core-wall, be carried to a very firm foun¬ 
dation in order to avoid settlement. Near the toes of the dam the 
weight is much less and a softer material will support it. For the por¬ 
tion to be occupied by the core-wall, if one is used, and a certain width 
in any case, the foundation must be excavated to an impervious stratum 
of solid rock or clay, and penetrate for a short distance such stratum. 
Where disintegrated and fissured rock is met with, the construction of 
a safe embankment requires the most careful work in preparing the 
foundation. In some recent cases trenches have been carried to depths 
of nearly 200 feet before a secure bottom has been reached. 

A sound bottom having been reached the surface should be 
roughened in order to give a better bond with the earth filling; and if 
the material is solid rock, all holes and crevices must be thoroughly 
cleaned and filled with cement or concrete. Springs of water met with 
on the foundation area are often very troublesome and dangerous, 
especially if under or near the core-wall- If flowing with a small head, 
they may be quite readily stopped up with concrete. If under con¬ 
siderable head, an attempt to smother them at first will likely cause 


33 6 


EARTHEN DAMS. 


them to break out at some other place. In such a case they are often 
dealt with by confining the water in a little well of concrete or in a 
pipe until a few feet of embankment have been built, then pumping out 
the well and quickly filling with concrete. Sometimes strong springs 
have been piped to the outside of the embankment, and this can safely 
be done where they occur in the down-stream portion of the dam, 
but this is otherwise a doubtful expedient. Whatever seepage-water 
gets through an embankment should run perfectly clear, as muddy 
water denotes a washing out of the material. 

397. Construction of the Embankment. —After the foundation has 
been prepared the trench is first filled with the material selected. If 
puddle, it should be placed in 4- to 6-inch layers well rammed, or 
cut and cross-cut with thin spades reaching well into the layer below, 
just enough water being used to render the material plastic. Where 
puddle is used in a narrow wall it is advisable to prepare it oefore 
placing by thoroughly pulverizing and tempering it with water, no 
more water being used than absolutely necessary. A pug-mill is very 
useful for this purpose, especially where artificial mixtures are em¬ 
ployed. Puddle should be thoroughly worked and homogeneous. If 
concrete is used, special care must be taken to secure thoroughly good 
work in mixing and ramming, and in filling all irregular spaces in the 
excavation. 

After the core is built to the surface, or a little above in the case 
of concrete, the main embankment is started. If the material used 
varies in quality, the finer and better should be placed above and 
adjoining the core-wall, and the coarser placed on the down-stream 
side and near the faces. If no core-wall is used, the better material 
should still be placed in the up-stream portion of the embankment. 
Stones exceeding 3 or 4 inches in diameter should not be allowed in 
the embankment except along the faces. The embankment is com¬ 
pacted usually by placing the material in layers 6 to 12 inches thick, 
wetting, and rolling with a heavy grooved roller weighing 200 to 300 
pounds per lineal inch. These rollers are often made by stringing 
cast-iron disks on an axle, the alternate disks being 2 or 3 inches 
different in diameter. Specially made rollers can also be had for this 
purpose. 

Much importance is attached to the work of compacting, and only 
by the best of supervision can good work be secured. The use of 
water should be just sufficient to render the material plastic and 
capable of being packed, and no more. An excess of water makes 
rolling more difficult and increases subsequent settlement. Many 


H YD RA ULIC D A M- CONS TR UCTION. 


337 


apply the water before the layer is placed, instead of afterwards, with 
good results. 

Embankments have been built of dry material, and if thorough 
ramming could be secured, this method would probably give a bank 
tighter and less liable to settlement than by the use of water. With 
some material, however, it is desirable to use a certain amount of water 
to reduce the lumps. If well-compacted, the settlement will be very 
slight, as small an amount as J inch in 50 feet having been reported 
by Mr. FitzGerald. With a masonry core-wall it is especially im¬ 
portant that the settlement of the embankment be small. 

During the construction of the main body of the embankment the 
core-wall if of puddle is carried up simultaneously therewith, thinner 
layers of material being used in this part, and more care in rolling. 
A concrete core-wall must be kept a few feet in advance of the earthen 
portion, and the latter well rammed against it. 

398. Hydraulic Dam-construction. —In the western part of the 
country many good embankments have been built by this method. 
The material is, where practicable, obtained from the adjacent hillsides, 
from which it is loosened by a water-jet and conveyed to the top of the 
dam by water flowing through pipes or flumes. There it is allowed to 
settle in a pond maintained by keeping the edges of the dam higher 
than the centre. The cost of construction where the conditions are 
favorable is exceedingly low. 

The following description of a dam constructed at Tyler, Texas, 
will further explain the process: * 

The dam is 575 feet long, 32 feet high, and contains 24,000 cubic 
yards, the inner slopes being 3 to 1 and the outer 2 to 1, with a 4-foot 
berme on the inside 10 feet below the top. All of the materials used 
in the dam were sluiced in from a neighboring hill at a cost of 4§ cents 
per cubic yard, including the plant and all the appurtenances of the 
reservoir. Water was pumped through a 6-inch pipe and directed 
against the hillside from a nozzle at a pressure of 100 pounds per 
square inch. The material washed down consisted of 65 per cent of 
sand and 35 per cent of clay. 

“ In beginning the work a^trench 4 feet wide was excavated through 
the surface-soil down into clay subsoil, a depth of several feet, and this 
was first filled with selected puddle clay sluiced in by the stream. 
Then the form of the dam was outlined by throwing up low sand ridges 
at the slope lines, which were maintained, as the dam rose in height, 


* From U. S. Geolog. Survey, 1896-97, pp. 654-5. 




338 


EARTHEN DAMS. 


by men with hoes. A pond of water was thus maintained over the top 
of the dam, the water being drawn off from time to time, either into 
the reservoir or outside as preferred. Ihe material was transported 
from the bank in a 13-inch sheet-iron pipe, with loose joints, stove-pipe 
fashion, extending from near the face of the bluff, where the jet was 
operating, across the centre line of the dam. These were so arranged 
as to be easily uncoupled at any point, so as to direct the deposit where 
required to build up the embankment uniformly. It was found that 
the quantity of solids brought down by the water varied from 18 per 
cent in solid clay to 30 per cent in sand. ” 

The entire cost of the dam with all its accessories is given at $1140. 
Mr. L. W. Wells was the engineer in charge. 

399. Slope Protection. —The up-stream slope must be protected from 
wave and ice action. This protection is usually afforded by a closely 
laid pavement about 18 inches thick laid on 6 to 12 inches of broken 
stone or gravel. Below low-water line a good layer of riprap is fre¬ 
quently substituted, the paving ending at a berme. The foot of the 
paving should be well supported by large blocks of stone or concrete. 
Where large gravel and boulders are abundant the face can be well 
protected by such material placed loosely, the larger stones being on 
the outside to resist the impact of the ice and waves. Paving should 
preferably not be put in place until all settlement has ceased. (For 
impervious linings see Chapter XXVII.) The down-stream face is 
usually sodded for sake of appearance and as a protection from rain, 
but may be protected by gravel and coarse material if more convenient. 
The edges of the embankment should have rounded rather than angular 
outlines. Where considerable seepage exists it is desirable to fill in at 
the outer toe to some depth with broken stone, as this aids in drainage 
and in maintaining the slope. 

400. Embankments and Foundations of Porous Material _Sand and 

ordinary porous earth have been successfully used in embankments of 
considerable size. In their construction it is necessary to bear in mind 
the effect of percolation on the stability, both in tending to wash out 
the material, and to decrease its effective weight. Percolation should 
in the first place be limited as far as possible, and to this end the em¬ 
bankment should be made broad and with flat slopes, especially on 
the lower face or the lower portion of the lower face. The upper slope 
may be made as usual if protected by paving. To prevent the mate¬ 
rial from washing out, the upper part should, if possible, be made of 
finer material than the lower, the change from one to the other being 
gradual. The velocity of the percolating water is thus much less in 



OUTLET-PIPES. 339 

the lower portion of the clam where the material is unsupported, but 
where the particles are larger and less easily moved by the water. 

If the foundation is also porous, as is apt to be the case, it is also 
necessary to prevent a high velocity of percolation through it. This 
is accomplished by the broad embankment which forces the water to 
pass farther through the material, and can also be aided by driving a 
line of sheet-piling along the center of the dam. The embankment 
must be spread out to reduce the load carried. To prevent the squeez¬ 
ing out of the foundation material, it may be excavated to a consider¬ 
able depth at both toes and replaced by gravel or concrete. It may 
also be desirable to load the earth to a considerable distance below 
the embankment proper by means of a low bank. Drainage at the 
outer toe is serviceable in lowering the line of saturation and main¬ 
taining a drier slope. 

Fig. 76 represents a standard Mississippi levee section and well 
illustrates the foregoing principles. 



Fig. 76. —Levee Section. 


A dike of ordinary top soil forms part of the Nashua Reservoir of 
the Boston Water-works. It is founded on very firm sand and has 
a maximum height of about 70 feet, with slopes of 4 to 1 on the 
up-stream side and 3 per cent on the lower face. The excessive width 
employed is partly due to the fact that the dike was a dumping-ground 
for the material stripped from the reservoir-site.* 

401. Outlet-pipes. —The design and construction of the outlet 
arrangements is one of the most important and at the same time most 
difficult features of the work. This is chiefly because of the difficulty 
of laying pipes or building masonry conduits through earth embank¬ 
ments in such a manner as to secure a perfect and reliable connection 
between the two materials. Poor work at this point is one of the chief 
causes of the many failures of earth embankments. 

In reservoirs of any considerable depth it is desirable so to arrange 
the outlets as to enable the water to be drawn off at different levels, not 
exceeding 10 or 15 feet apart, in order that water of the best available 
quality may at all times be obtained. Provision must also be made 

* Report Mass. Board of Health on Metropolitan Water-supply, 1895, p. 134; 
also Eng . Record , 1900, XLI. p. 5 °* 










340 


EARTHEN DAMS. 


by suitable gates or valves for controlling the flow or turning it into a 
conduit or other channel; and to make the operation as reliable as 
possible, all valves or other working parts should be readily accessible. 

The outlet-pipes are usually of cast iron and may either be laid 
underneath the embankment and surrounded thereby, or a culvert of 
masonry may be constructed in the embankment and the pipes laid 
therein, or they may be laid in a tunnel constructed in the natural 
ground at the end of the embankment or at some more remote point 
in the reservoir. A gate-chamber containing the necessary valves is 
located at some point along the outlet-pipe or conduit. The size of 
the pipe must be such as to deliver water at the required rate without 
too great loss of head as determined by considerations of economy, or 
by the head available when drawing from the lowest desired level. 
This will usually limit the velocity to 4 or 5 feet per second. For 
large quantities two or more outlet-pipes are used. 

402. Pipes Placed in the Embankment. —In the case of reservoirs 
with comparatively low embankments the outlet-pipes are usually laid 
beneath the embankment at or near the lowest point. They should 
be laid on a good firm foundation in the natural ground, and should 
preferably rest upon and be surrounded by a bed of 8 to 12 inches of 



Fig. 77. —Section through Outlet-pipe, Minneapolis Reservoir. 

rich concrete, well rammed into the trench and left rough on the out¬ 
side. To enable the earth to be more thoroughly bonded with the 
concrete, cut-off walls should be built projecting out from the main 
body of the concrete, i-J to 2 feet, as shown in Fig. 77. If concrete is 
not used, then the pipes should be provided with wide flanges about 
which puddle cut-off walls should be built in the most careful manner. 
The pipes should be very carefully laid and tested under pressure 
before covering. 

If the embankment has a masonry core-wall, a good secure connec¬ 
tion can readily be made at this point between pipe and embankment. 





















































































OUTLET-PIPES. 


341 


If the core is of puddle, great care must be taken in thoroughly ram¬ 
ming the puddle about the concrete. If the trench extends below the 
pipe, it should be filled underneath with concrete rather than puddle, 
as otherwise settlement and rupture are very liable to occur. The 
great difficulty of securing reliable work at this point, and the failures 
which have occurred, have led many English engineers to strongly 
favor the use of tunnels. 

403. Culverts. —For some reasons an open culvert is much to be 
preferred to a pipe. Once constructed, additional pipes may be laid 
therein at any time; the pipes may also be readily inspected, and any 
leaks that occur in them do not endanger the structure, a matter of 
especial importance where the pipes are under heavy pressure. The 
culvert may also be conveniently made to act as a wasteway for the 
stream during construction. 

The same precautions must be taken in the construction of culverts 
as in the laying of pipes. They must have a good firm foundation and 
a good bond with the surrounding embankment. The cross-section 
must be amply strong to resist all lateral and vertical pressures, the 

4 

latter being assumed to act upwards as well as downwards, and, in the 
upper portion of the embankment, to be equal to the full water-pressure 
of the reservoir. The material ordinarily employed is brick, or con¬ 
crete with a lining of brick. Imperviousness is secured by the use of 
a rich mortar and by plastering on the outside with Portland-cement 
mortar neat or 1 to 1. Cut-off walls or projecting courses should be 
built around the outside at intervals as described for pipe outlets. At 
the connection with the gate-house a cut-off wall is put in through 
which the pipes pass, and which must sustain the full head of water. 

Fig. 78 illustrates a culvert constructed through an embankment 
of an impounding-reservoir, with outlet-pipes laid therein and opening 
into a gate-chamber at the ‘upper toe. Where the gate-chamber is 
placed just above the core, the culvert may stop at that point and pipes 
be used to conduct the water from reservoir to gate-house. Where the 
water is turned into the natural watercourse below, the pipe may be 
dispensed with, the water passing through the open culvert. 

The outlet arrangements of the new settling reservoirs for Cincin¬ 
nati are shown in Fig. 79. Here the culvert is constructed in the 
natural ground and has a very heavy section. A J-inch coat of Port- 
land-cement plaster on the outside insures imperviousness. 

404. Tunnels. —If a tunnel be used, it may be made straight and 
pass underneath the embankment, or may turn an angle and pass 
around it altogether (the gate-chamber being placed at the angle), or 


342 


EARTHEN DAMS, 


it may cut through a narrow place in the divide and lead the water into 
another valley, a rare but very favorable arrangement. With deep 



puddle trenches or soft foundations it is desirable to entirely avoid 
cutting into or under the dam. 

If the material through which the tunnel passes is anything but 





































































































































GA TE■ CHA MB EES. 


343 


hard impervious rock, the tunnel must be lined with brick, and back of 
the lining the excavation must be thoroughly filled with concrete. In 
rock a tunnel is entirely satisfactory, but in earth it is difficult to avoid 
disturbing the strata, and the back-filling is much more difficult than in 
the case of a culvert constructed in open trench. Sometimes in solid 
rock a trench instead of a tunnel is dug around the end of the dam, and 
the gate-chamber located therein. 

405. Gate-chambers.—The gates or valves controlling the flow 
through the outlet-pipes are placed in small masonry chambers, which, 
besides allowing of convenient operation of and access to the valves, 
also usually contain screening-chambers and valve arrangements 
whereby water may be drawn from different levels. 

406. Position of the Gate-chamber .—Gate-chambers are preferably 
placed at or near the upper end of the outlet-pipes in order that the 
pressure therein may be under control. They are, however, sometimes 
placed at the outer toe of the embankment, but this is undesirable, as 
it is impossible to shut off the water from the pipes in case of leakage 
except by the use of divers. This point is of more importance with 
large dams than in the case of small distributing reservoirs. In dams 
with core-walls the gate-chamber may properly be placed anywhere 
between the core-wall and upper toe, and with core-walls of masonry 
it is conveniently placed just above and adjoining the masonry core. 

An advantage gained by placing the chamber at the inside toe is 
that it enables arrangements to be easily made for drawing water from 
different levels. Fig. 78 shows a gate-chamber in this position. A 
foot-bridge is here necessary to allow of access to the gate-house. 
This position exposes the chamber to severe stresses from the action of 
ice and is therefore more suitable for large than for small structures. 
If the chamber is placed farther back in the embankment, the necessity 
of a bridge is avoided and the structure is much better protected from 
the action of ice, but the drawing of water from different levels is not 
so convenient. It may be drawn from the bottom by a continuation 
of the outlet-pipe or culvert to the upper face of the embankment, as 
in Fig. 77. It can also be drawn from near the top by an inlet in the 
masonry wall or by a short inlet-pipe. To draw from intermediate 
levels, inlet-pipes or sluices must be extended to the face, as in Fig. 
81 ; or an adjustable inlet-pipe may be employed, as is common with 
distributing-reservoirs and as illustrated in Fig. 79; or the embankment 
may be removed from the upper face of the chamber and supported on 
the sides by heavy wing walls, thus enabling the water to be drawn 
through ordinary sluiceways. This last method becomes very expen- 


344 


EARTHEN DAMS. 


sive with high embankments. In Fig. 81 the first and last methods 
are combined. 

407. General Arrangements .—The various forms of gate-chambers 
may be further described in connection with the examples illustrated by 
the figures. The simplest form is shown in Fig. 77, page 340, and 
consists merely of a single chamber built over the valve in the single 
outlet-pipe. A separate waste-pipe is here provided. The illustration 
refers to a distributing reservoir, but the arrangement is suitable for 
small reservoirs where screens are not required and where it is neces¬ 
sary to draw water from but one level. 

Fig. 80 illustrates a design suitable for small reservoirs. This 




Fig. 80.— Gate-chamber, Ipswich, Mass. (Goodell.) 


arrangement permits of drawing water from near the bottom and from 
about mid-depth. Screening is also provided for. 

Fig. 81 illustrates a form adapted to larger works and shows how 
pipes may be arranged to draw from different levels when the gate- 
chamber is placed in the body of the embankment. Grooves are pro¬ 
vided for screens and for stop-planks for regulating the flow from the 
surface of the reservoir. A waste-pipe is shown and also an overflow, 
































































G A TE- CHA MB EES. 34S 

the reservoir in question being a distributing-reservoir.* (See Chapter 
XXVII for further details of distributing-reservoirs.) 

In Fig. 78 is shown a still more elaborate gate-chamber suitable 
for the largest reservoirs, and similar to that used in some of the reser¬ 
voirs of the New York and Boston Water-works. (See also Fig. 99, 
page 378.) The structure is divided longitudinally into two cham¬ 
bers. The division-wall contains the sluice-valves for drawing water 
at different levels, admission to the outer chamber being through large 
openings placed opposite the valves. In the outer chamber are grooves 
for screens which may also be used for wooden stop-planks in case of 
emergency. As an additional measure of safety the upper end of the 




Fig. 81.—Outlet-chamber, Syracuse Water-works. 


inlet-pipe may be provided with a valve as shown. At the lower face of 
the dam is usually placed another valve-chamber containing valves for 
directing the flow into waste-pipes, or into a conduit, or otherwise, as 
the case may be. This also provides a more convenient place foi the 
daily regulation of the flow. Where there are two or three outlet-pipes 
the chamber is divided into a corresponding numbei of divisions, each 
of them arranged to be operated independently. A piefeiable anange- 
ment to that shown would be to place the gate-chamber just above the 
core-wall, which is the usual Boston practice. One of the methods 


* Trans. Am. Soc. C. E., 1895, xxxiv. p. 46. 











































































































































346 


EARTHEN DAMS. 


described in Art. 406 would then have to be adopted if water is to be 
drawn from different levels. 

Fig. 82 illustrates a large gate-chamber on one of the distributing- 
reservoirs of the New York Water-supply. This design combines 
many of the desirable features already mentioned. Note that access 
is had to the pipe-line from the gate-chamber. 

A form of inlet-tower used much in English practice is shown in 


Fig. &2.—Jerome Park Gate-house. 

(From Wegmann’s “ Water-supply of New York.”) 



***<&%& 


EMBANKMENT 


RESERVOIR 




Fig. 83.—Inlet-tower, Glasgow Water-works. 


Fig. 83. It consists of but a single chamber, the inlets being placed 
at various levels. A separate screen-chamber is built on shore.* For 
towers having a single chamber the circular form is to be commended. 

Arrangements differing considerably from those above described 
have also been used with satisfactory results. The proper one to adopt 


* Engineering , 1894, LVII. p. 73S. 





































































































































GA TE-CHAMBERS. 


34 7 


in any particular case depends upon local conditions and is determined 
by considerations of safety, economy, and convenience of operation. 

Gate-chambers are sometimes entirely dispensed with, and the 
sluice-gates built into the sloped embankments, with rods for operating 
them carried up the inclined face to mechanism above. This arrange¬ 
ment is suitable only in mild climates where trouble with ice is not to 
be feared. It is cheap, but not as reliable or as convenient in case of 
stoppage as the gate-chamber. 

408. Details .—The masonry of the inlet-tower is usually of heavy 
rubble, faced with ashlar and lined with hard brick or cut stone. It 
should be laid in rich Portland-cement mortar to secure imperviousness. 

The thickness of walls is a matter determined by judgment and 
experience. The tower as a whole when located at the toe must be 
able to resist ice and wave action, and each wall the unbalanced 
pressure of the water. A circular tower is the best form as regards 
stability. The walls will vary in thickness with their unsupported 
length, or the size of interior chamber, but the exterior walls are 
usually made 3 to 4 feet thick at the top, with an increase of about 
three-fourths inch to 1 inch in thickness per foot of depth, the batter 
being made on the outside for convenience and to furnish a better bond 
with the earthwork. Interior walls may be made of slightly less 
thickness. 

The foundation should be prepared with great care. If the gate- 
chamber is placed near the toe, the load will be much heavier than the 
surrounding earth embankment, and unequal settlement is liable to 
occur, causing cracks in the masonry of the culvert and displacing the 
outlet-pipes. The bottom of the gate-chamber should be constructed 
under the supposition that full water-pressure will exist underneath the 
chamber when empty. It is best made of concrete and lined with brick 
or stone. 

Fish-screens are usually copper-wire screens with •§• to J inch mesh, 
fastened to wooden or iron frames and arranged to slide in grooves in 
the masonry. They are arranged in pairs, and each screen is made up 
of several elements of a size convenient to handle.* 

The gate-chamber is surmounted by a gate-house in which is 
located the operating mechanism of valves and screens. As this build¬ 
ing is frequently quite prominent, it is important that it be given an 
artistic treatment suited to the surroundings. Two very commendable 
designs are illustrated on page 349, and show what may be done in 

* For details of screen and mechanical lifter used at distributing-reservoirs of 
the Boston water-works, see Eng. News, 1900, xliv. p. 21S. 




348 


EARTHEN DAMS. 


this direction. The former illustration is taken from Wegmann's 
^ 4 Water-supply of New York,” and the latter is from a photograph 
loaned to the authors by the engineer, Mr. L. M. Hastings. 

The bottom of the reservoir should be paved near the gate-chamber 
and the lower sluiceway placed close to the bottom; or a separate 
drain-pipe may be provided as shown in the illustrations. This is a 
necessary feature in small distributing-reservoirs requiring frequent 
cleaning. If the gate-chamber is not located at the very bottom of the 
valley, a drain-pipe may lead to such point and be operated as a siphon 
when it is desired to drain the reservoir. Where much sediment is 
deposited it is desirable to have a large sluice-gate at the \ery bottom 
to use in flushing out the material near the dam. 

409. Valves and Sluice-gates.—The inlets into the gate-chamber 
are made to correspond in size with the outlet-pipe. For small inlets 
the most convenient form is a small piece of pipe built into the walls 
with an ordinary gate-valve attached thereto, as shown in Fig. 81, or 
a small sluice-valve as shown in Fig. 80. Large valves require a good 
broad support, and in narrow walls and chambers it is more convenient 
and also cheaper to use in most cases cast-iron sluice-gates of the latter 
form. These large gates are usually of special design, made with 
ribbed faces on the side towards the water-pressure, and plane on the 
other side, as is ordinarily done with cast-iron plates. The gate is 
made to slide in grooves faced with brass or bronze, and the sliding 
surfaces of the gate are similarly faced. 

Where the water-pressure tends to force the gate off its seat, some 
form of wedge arrangement must be used to force the gate to its seat 
when nearly closed. Such an arrangement is shown in the gates of 
the St. Louis intake (Fig. 43, page 255), the wedge being formed by 
an additional groove with brass facing. Instead of a continuous 
inclined groove such as this, a series of adjustable blocks is sometimes 
employed against which bear corresponding projections on the back of 
the gate. When the pressure holds the gate to the face a simple 
groove is sufficient. 

The frame of the gate is usually of cast iron, bolted securely to the 
masonry, in which case the opening is lined with cut stone; or cast- 
iron pipes or sluices may be built in the masonry and at the same time 
serve as attachments for the frames. The latter method is employed 
.at Syracuse, and Fig. 86 illustrates the sluice-gate there used.* 

Small sluice valves are operated by hand-wheel, larger ones by 


* Trans. Am. Soc. C. E., 1895, xxxiv. p. 27. 







New York 


(Wegmann.) 


Central Park Gate-house 




Fig. 85.— Payson Park Gate-house, Cambridge. 


349 













WASTE- WE ITS. 


351 


worm-gearing proportioned according to the pressure and available 
power. When convenient, hydraulic power, using a mixture of water 
and glycerine, as at St. Louis and Cincinnati, is very suitable, each 
cylinder being readily proportioned according to the load. The 
cylinders can be so arranged that in case of failure of the pressure 
they may be operated by a hand-pump. 

410. Waste-weirs.—As already noted, one of the most fruitful 
causes of reservoir failures is insufficiency of waste-weir capacity, 
resulting in the overflowing of the dam and its rapid destruction. 
Mention need only be made of the terrible Johnstown disaster in 1889, 



Fig. 86.—Slutce-gate, Syracuse Water-works. 



where, on account of insufficient wasteway, an earthen embankment 
was destroyed, resulting in the loss of over 2000 lives and the destruc¬ 
tion of property valued at 3 to 4 million dollars.* 

In Chapter VI the subject of maximum flood-flows was fully dis¬ 
cussed. The maximum flood having been estimated, it remains to 
provide some safe means whereby it may be passed to the valley below. 

This is done in three different ways: (1) A wasteway may be 
excavated in the natural ground at one or both ends of the dam. 
Where the foundation is of rock this is a very safe and effective form of 

* See Report of Investigating Committee in Trans. Am. Soc. C. E., 1891, xxiv. 
P- 431- 





























































352 


EARTHEN DAMS. 


wasteway, but care must be taken to have it of sufficient slope and 
cross-section at all points to carry the required amount of water at the 
assumed depth. On earth foundations the slopes of such a channel 
would need to be thoroughly protected with heavy solid masonry in 
cement. It will, however, seldom be economical to construct a waste¬ 
way of this kind in earth. 

(2) The waste way may sometimes be formed at some low point in 
the dividing ridge, and the water led to another valley. This is likely 
to require considerable attention in providing a safe channel for the 
increased quantities of water carried in the other valley, particularly at 
its upper end. 

(3) The third form of wasteway is provided by making a portion of 
the dam of masonry designed as a spillway, and placed at about the 
axis of the valley. The forms of such dams are discussed in detail in 
Chapter XVII. At the junction of the masonry and the earth portions, 
the lower slopes of the embankments must be retained by heavy wing 
walls built out from the masonry dam. The upper slopes may be like¬ 
wise protected, or they may be carried around in front of the masonry 
weir throughout its entire length. Where the earth and masonry por¬ 
tions join, great care must be taken to ram the earth solidly in place. 
Particular attention should also be given to the connection between 
core-wall and masonry. The back of all walls touching the earth 
should be left rough and be built with a batter. The advantage of a 
masonry core-wall is here obvious. Fig. 99, page 378, shows the plan 
of wing wall at the junction of a weir and an earthen embankment 
which well illustrates the foregoing points. 

411. P roportions of Waste-weirs .—The requisite capacity being 
known, the length and depth of weir are to be determined. Either may 
be assumed and the other computed by means of a weir formula, but 
in each case there are certain proportions that will be the most 
economical. A low weir requires a greater length, whereas a deep 
and short weir requires, for the same storage volume, that the rest of 
the dam be made higher. The proper proportions are thus dependent 
upon the relative cost of weir length and of extra height of dam, and is 
largely a question of topography. Weir heights will ordinarily range 
from 2 to 4 or 5 feet, with lengths of 50, 100, or even 500 feet, or more, 
depending on the required capacity. In any case the flood line deter¬ 
mines the height of the other part of the dam, while the weir crest 
determines the storage. The difference is the available depth of weir. 
For weir formulas see Chapter XII. 

412. Care of Floods during Construction.—One of the most trouble- 



LI TER A TURK. 


353 


some and expensive features of construction is the provision for passings 
the floods over or through the works. At the start an artificial channel 
or flume can readily be constructed at one side of the valley, and the 
culvert or outlet-pipe put in place, if there be such. The ordinary dis¬ 
charge and moderate floods can then be passed through this. Heavy 
floods may be allowed to pass over an uncompleted masonry weir or 
be carried over the embankment at a point protected by timber aprons. 

In constructing the Titicus dam of the Croton Water-supply the 
river was first turned into an artificial channel by means of a temporary 
dam 24 feet high and about 1000 feet above the main dam. Afterwards 
a timber flume was used having two compartments, each 9 feet by 7 feet 
9 inches, placed 25 feet above ground where it crossed the dam. After 
the dam was raised above the flume, the water was turned into the 
gate-house and discharged through two outlet-pipes 48 inches in 
diameter. Extreme floods were allowed to pass over the uncompleted 
portions of the masonry wasteway at a low point left for the purpose. 
It was considered that the damage thus caused was less than the 
expense of constructing a flume large enough to carry the water. Two 
heavy freshets were thus taken care of. The tributary area was 22.8 
square miles.* 

413. Cost.—The cost of reservoir embankments when constructed 
in the usual way will range about as follows: Excavation 25 to 30 cents 
per cubic yard; embankment 30 to 40 cents; puddle 50 to 75 cents; 
dry paving $2.00 to $3.00; riprap $1.50 to $2.00; sodding 20 to 30 
cents per square yard. For the cost of various classes of masonry see 
Art. 449 of the next chapter. 

LITERATURE. 

(See also Chapter XXVII.) 

CONSTRUCTION. 

1. Dorsey. Excavation and Embankment by Water-power. Trans. Am. 

Soc. C. E., 1886, xv. p. 348. 

2. Henzell. The West Hallington Reservoir. Proc. Inst. C. E., 1890, 

cii. p. 271. 

3. Follett. Earthen vs. Masonry Dams. Eng. News , 1892, xxvn. p. 20; 

Eng. Record , 1892, xxv. p. 400. 

4. Dam No. 5 for the Additional Water-supply of Boston. Eng. News , 

1895, xxxiii. p. 230; Eng. Record , 1893, xxvm. p. 361. 

5. The Monument Creek Reservoir, Colorado. Eng. News, 1893, xxix. 

P- 2 35 - 


* Wegmann’s Water-supply of New York, p. 200 





354 ear then da ms. 

6. Herschel. The Works of the East Jersey Water Company, for the Supply 

of Newark, N. J. Jour. New Eng. W. W. Assn., 1893, vm. p. 18. 

7. Le Conte. High Earth Dams. Proc. Am. W. W. Assn., 1893, p. 142. 

8. The Use and Abuse of Water in the Construction of Reservoir Embank¬ 

ments. Valuable Discussion. Jour. Assn. Eng. Soc., 1894, xm. 
p. 156. 

9. Norboe. The Honey Lake Valley Dam, Cal. Eng. News , 1894, xxxi. 

p. 217. 

10. Gould. The Dunnings Dam. Trans. Am. Soc. C. E., 1894, xxxn. 

p. 389. 

11. Freeman. Hoisting Apparatus of the Canal Headgates at SewalPs Falls, 

N. H. Trans. Am. Soc. C. E., 1894, xxxn. p. 278. 

12. The Glasgow Water-works. Engineering , 1894, lvii. p. 461. 

13. Taylor. The Construction of Reservoir Embankments. Jour. New Eng. 

W. W. Assn., 1894, vm. p. 130. 

14. Dumas. Etude sur les Barrages-Reservoirs. Le Genie Civil, 1895, 

xxvii. p. 280. 

15. Hill. The Water-works of Syracuse, N. Y. Trans. Am. Soc. C. E., 

1895, xxxiv. p. 23. 

16. Fortier. Earthen Dams. Bulletin No. 46, 1896, Utah Agricultural 

Experiment Station. 

17. The Water-works of Colorado Springs and the Strickler Tunnel. Eng. 

News , 1896, xxxvi. p. 131. 

18. Watts. Notes on Sinking, Timbering, and Refilling Concrete and Puddle 

Trenches for Reservoir Embankments. Paper before Brit. Assn. 
W. W. Engineers. Eng. Record, 1897, xxxv. p. 406. 

19. Paskin. Discharge Tunnels from Reservoirs. Paper before Brit. Assn. 

W. W. Engineers. Eng. Record , 1897, xxxv. p. 426. 

20. Difficulties with Earth Dams in Great Britain. Abstract of a Paper by 

W. Fox before the Soc. Engineers. Eng. Record , 1898, xxxvm. 
p. 290. 

21. The Wachusett Reservoir and Aqueduct. Eng. Record , 1898, xxxvn. 

p. 405. 

22. The Kingston, N. Y., Water-works. Eng. Record, 1898, xxxvn. p. 341. 

23. Coppee. Standard Levee Sections. Trans. Am. Soc. C. E., 1898, 

xxxix. p. 191. 

24. Strange. Reservoirs with High Earthen Dams in Western India. Proc. 

Inst. C. E., 1898, cxxxn. p. 130; Eng. Record, 1899, xxxix. 
p. 448 . 

25. The Water-works of Plymouth, England. Eng. Record, 1899, xxxix. 

p. 181. 

26. Knight. Flood-water Channel, Altoona Reservoir. Jour. New Eng. 

W. W. Assn., 1899, xiv. p. 151; Eng. Record, 1899, XL * P- 386. 

27. The Wachusett Reservoir. Eng. Record, 1900, xli. p. 50. Stripping 

of the reservoir and construction of the large dike. 

FAILURES, ETC. 

1. Failure of the Dale Dike Reservoir. From Rawlinson’s Report. Van 

Nostrand’s Eng. Mag., 1869, 1. p. 263. 

2. The Failure of the Worcester Dam. Eng. News, 1876, 111. p. 116; Van 

Nostrand’s Eng. Mag., 1877, xvi. p. 54. 


LITERATURE. 355 

3. The Failure of a Reservoir at Cleveland, 0 . Eng. News , 1886, xvi. 

p. 422. 

4. Evans. Beacon Street Reservoir, Lowell Water-works. Jour. Assn. 

Eng. Soc., 1886, v. p. 297. 

5. Slipping of the Slope Paving of the Beacon Street Reservoir at Lowell, 

Mass. Eng. Record , 1886, xm. p. 154. 

6. Lukens. Some Remarkable Breaks in a Reservoir. Proc. Eng. Club 

Phil., 1887, vi. p. 147. 

7. Report of Committee of Am. Soc. C. E. on the Cause of the Failure of 

the South Fork Dam. Trans. Am. Soc. C. E., 1891, xxiv. p. 431. 

8. Expert’s Report on the Reservoir Failure at Lancaster, Pa. Eng. News, 

1894, xxxii. p. 462. 

9. The Reservoir Break at Portland, Me. Jour. New Eng. W. W. Assn., 

1894, viii. p. 148; Eng. News, 1893, xxx. p. 140; Eng. Record, 
1893, xxviii. p. 186. 

10. Report on Defects in the Queen Lane Reservoir, Philadelphia. Eng. 

News, 1895, xxxiv. p. 102. 

11. The Failure of the Distributing Reservoir of the Water-works of Grand 

Rapids, Mich. Eng. News , 1900, xliv. p. 25. 


CHAPTER XVII. 


P 

l 


MASONRY DAMS. 

THE DESIGN. 

414. General Conditions. —Dams of masonry can safely be built only 

upon very firm foundations. Low dams of a height of 20 or 30 feet, 
and occasionally higher, have been founded on firm earth, but high 
masonry dams should be constructed on nothing less substantial than 
solid rock. In any case it is necessary to prevent practically all settle¬ 
ment, for with a material such as masonry any appreciable settlement 
is quite certain to cause cracks. Given, however, a firm foundation, a 
masonry dam is much superior to an earthen embankment in several 
respects. Its design can be more certainly and precisely determined 
upon; it is more durable; outlet pipes and conduits can be constructed 
through it with much greater safety; and, when properly designed, 
flood-waters may pass over it without danger to the structure. For 
very high dams, such as those above 100 feet, masonry is much to be 
preferred. As regards economy, the masonry dam may even be 
cheaper in some cases than one of earth, this question depending 
mainly upon the convenience of obtaining suitable material. 

Earthen dams are largely designed according to empirical rules, 
but with a solid material such as masonry it is possible to apply to a 
considerable extent the principles of mechanics in determining the 
proper forms. Moreover, as masonry is a relatively expensive 
material, it is very desirable for the sake of economy to make the 
theoretical investigation as thorough as is consistent with the accuracy 
of the data. 

415. The External Forces Acting upon a Dam. —Dams are built either 

straight or curved in plan. In the former case, it is assumed that all 
forces act in a plane perpendicular to the dam, and that the dam resists 
by gravity alone; in the latter case, arch action may exist to a greater 
or less extent, thus involving other than normal forces. The first case 

356 


FORCES AND STRESSES. 


35 7 



only will be here treated, and it will be sufficient to consider a length 
of dam of one unit. (For a discussion of the curved form see Art. 

433 -) 

The principal external forces acting upon an impervious dam, 
A BCD (Fig. 87), resting upon an impervious base are, the water- 
pressure P y the weight of the masonry G , and the 
reaction R . In addition to these forces, certain 
others require consideration, such as ice and wave 
pressure near the top, wind pressure, and back 
pressure of water on the side BD. Furthermore, if 
the dam or foundation is more or less porous, a cer¬ 
tain amount of uplift will exist to reduce the effective 
weight Gy as shown in Art. 378. However, with 
good mortar joints and good material for a founda¬ 
tion this uplift will be very small. It will for the Fig * 8 7 * 
present be neglected, as is the usual practice, but this and the other 
forces mentioned will be considered later. 

Assuming only the three forces Py G y and R as acting, they are 
all readily determined for any given section. 

416. Internal Stresses.—In order to investigate the internal stresses, 

pass any horizontal section mn 

fo; through the dam and consider the 
r portion ABEF (Fig. 88). Repre¬ 
sent here the external forces by P 
^ and Gy quantities readily determin¬ 
able ; and the internal stresses on the 
section which are necessary for equi¬ 
librium, by the two components V 
^ and H. The resultant of all vertical 
stresses on the section, tension and 
compression, is thus represented by 
Vy and H is the resultant shear. 

The distribution of these direct and shearing stresses is yet to be deter¬ 
mined. 

417. Ordinary Assumptions as to Stress Distribution. —As regards 
V it is assumed, first, that the stress varies uniformly across the sec¬ 
tion, as in the ordinary theory of beams, retaining-walls, etc. If e is 
the eccentricity of V (distance from the centre of EF)y the stress upon 
the section may be considered as due to a compression F, uniformly 
distributed, plus a stress due to the moment Ve. The maximum com¬ 
pressive stress will then be at E } and, as in a beam, will be equal to 



Fig. 88. 














































358 


MASONRY DAMS. 


V Mv. V 

f-= T +-? = T+V‘-j 3 ' = 

At E the stress would be equal to 


£ 
2 

tV 




Vf 6 e\ . 

/min- = ~J\ l “ V ).^ 

So long as e is less than ~- f or the resultant V remains within the 

middle third of /, compression exists at all points and the distribution 

/ 

of stress is as represented in Fig. (a). If e = g, then the stress at E 

2 V 

is zero, and at F is —, or double the average, as in Fig. (b). If e is 


l 


greater than g 


then by the formula there would be tension at E. 


In 


masonry structures the tensile strength is not to be relied upon, and it 
is therefore assumed that there is no tensile stress. The distribution 
would then be as shown in Fig. (c), and the entire load would be 


carried by a length of joint equal to 



The stress at F would 



The shear H is not usually considered except as requiring a suffi¬ 
cient frictional resistance along the plane EF. 

418. Errors Arising from the Ordinary Assumptions .—There are 
two sources of error in the above method of treatment. One is due to 
the assumption that the maximum intensity of stress is in a vertical 
direction. It will really be inclined, and greater than as above figured, 
its amount and direction at any point depending upon the intensities 
of V and H at that point. It will vary from the vertical direction both 
on account of the inclination of the resultant of V and H (R) t and on 
account of the inclination of the exterior faces of the dam. At the 
points E and F the direction of the maximum compressive stress must 
be parallel to the respective faces, while at intermediate points it will 
vary between the two extremes. Even were the material homogeneous 
it would be impossible to determine these compressive stresses and 
their direction, but the lines of maximum pressures would probably be 
somewhat as shown in Fig. 89, 








CONDITIONS OF STAB III TV. 


359 


To allow for the inclination of R some writers use, instead of V, the 
force R, and consider it as acting on a plane equal in length to the 

projection of EF parallel to R. This is equivalent to using —in 

cos 2 a 

place of V as above, where a is the angle of inclination of R with the 




Fig. 90. 


vertical. This assumes that the resistance of the masonry is due 
entirely to compressive stress on the inclined surfaces perpendicular 
to R (Fig. 90), and neglects the shearing stress on the other surfaces. 
It also does not take into account the effect of the inclined faces of 
the dam in varying the direction of the internal stresses, which alone 
would make the local stresses inclined at the faces even though the re¬ 
sultant R be vertical. The most common method of treatment is to 
use V only, and to allow something for the greater intensities of stress 
in an inclined direction by using a lower working intensity for the 
down-stream face. 

The other error in the ordinary theory is the assumption that the 
pressures are uniformly varying. For a section like a high masonry 
dam the greater length of the outside toe renders that portion some¬ 
what more elastic than the other part, thus tending to reduce the stresses 
at this point and to increase them elsewhere. Whatever this effect 
may be, it is on the side of safety. 

419. Conditions of Stability. —Considering any section EF, as in 
Fig. 88, the conditions usually imposed to secure stability are three: 

(1) The maximum compressive stress due to V at F or at F shall 
not exceed safe limits. 

(2) There shall be no tensile stress at any point of the section. 
This requires, as shown in Art. 417, that the resultant of V and H or 
of P and G shall not cut the section outside its middle third. 

(3) The resistance to shearing or sliding shall be greater than the 
total horizontal force at the level of the joint. 

Another condition is sometimes stated as an independent one, 
namely, that the dam shall not overturn; but if condition (2) is met, 
there can be no possibility of overturning. When the resultant pres¬ 
sures for reservoir full and reservoir empty both cut the edge of the 








360 


MASONRY DAMS . 


middle third, the factor against overturning is 2. All of the above 
conditions must be fulfilled at the foundation as well as at all sections 
of the structure, and if the foundation material is less strong than the 
masonry of the dam this must be allowed for under (1) and (3). 

Besides these conditions of stability that of imperviousness is of 
course understood, although this requirement is not absolute, but 
merely relative. 

420. Resistance to Shearing or Sliding .—To fail by sliding on a 
horizontal joint, or a succession of horizontal and vertical joints, the 
cohesion of the mortar must be overcome as well as the friction. The 
latter is, in the body of the dam, nearly always more than sufficient 
for stability. That the cohesion of the mortar is also to be largely 
counted upon is shown by the stability of numerous concrete dams, 
where the mortar must not only resist shearing on a horizontal plane, 
but on planes inclining outwards and downwards, on which the intensity 
of stress is much greater and the friction much less. By limiting the 
compressive stress we at the same time provide for shearing stresses, 
and they need not be further considered. 

At the base of a dam the sliding tendency must be well looked 
after. Where the foundation is clay, or perhaps a timber platform, 
special precautions will be needed. Table No. 59 contains coefficients 
of friction which will be useful in this connection. They are from 
Baker, Fanning, and others. With rock foundations the conditions 
will be similar to those in the body of the structure if the masonry be 
well bonded to the bed-rock. 

TABLE NO. 59. 

COEFFICIENTS OF FRICTION OF VARIOUS MATERIALS. 

Material. 

Granite (roughly worked) on gravel and sand (wet). 

Pine (sawed) on gravel and sand (wet). 

Granite (roughly worked) on sand (dry). 

“ “ “ (wet) .7.'.’.’.’.’.!!'.!! 

Masonry, on clayey gravel. 

“ “ dry clay. 

“ “ moist clay. 

Point-dressed granite (medium) on like granite. 

4 < << 4 « 4 4 4 i ^ 1*1 . 

common brickwork. 

4 4 n 4 < 4 4 4 4 .1 

smooth concrete. 

Fine cut granite (medium) on like granite. 

Dressed hard limestone (medium) on like limestone. 

( ( 4 4 « 4 44 441_*1 1 

brickwork. 

Beton blocks (pressed) on like Beton blocks. 

Common bricks on common bricks... 

“ “ “ dressed hard limestone. 


Coefficient. 
. O.41 
. O.41 
. 0.65 

• 0.47 

• 0.577 
. O.510 

• O.325 
. 0.70 

. o 63 
. 0.62 
. 0.58 

• O 38 
. 0.60 
. 0.66 
. 0.64 
. 0.60 


















STABILITY OF LOW DAMS. 


361 


421. Allowable Pressure.—This will depend upon the kind of 
masonry adopted. With large rubble masonry, as ordinarily employed, 
the safe pressures are taken all the way from 8 to 15 tons per square 
foot. With first-class concrete a pressure of 8 to 10 tons maybe used. 
Many of the existing high dams sustain maximum pressures equal to 
the latter figures, and several exceed 14 tons. The Vyrnwy Dam has 
a maximum pressure of 8.7 tons. The Quaker Bridge Dam was 
designed for a maximum of 16.6 tons, and the new Croton Dam has 
practically the same profile. The Periyar Dam, Madras, of concrete, 
sustains 8 tons. The San Mateo concrete dam sustains a pressure, 
reservoir full, of about 7.7 tons, and 10 tons with reservoir empty. 

422. Weight of Masonry.—The specific gravity of rubble masonry 
or good concrete is usually taken at from 2 \ to 2^, corresponding to 
weights of 140 and 156 pounds per cubic foot. The latter value was 
adopted in designing the Quaker Bridge Dam, experiments giving 
1 56.5 pounds. In the Sweetwater Dam it was estimated at 164 
pounds, the stone being very dense and joints narrow. Concrete 
blocks cut out of the Vyrnwy Dam had a specific gravity of from 2.48 
to 2.55. 


A. Stability of Low Dams. 

423. Conditions of Stability.—Dams up to 30 or 40 feet in height 
are usually made trapezoidal in form, the saving obtained by making 
the faces curved or broken not being enough to justify the extra 
trouble. For such low dams the only condition of stability requiring 
consideration, besides that of friction on the base, is that of tension in 
the joints. This requires that the resultant pressure shall keep within 
the middle third ; for economy, it should just cut the edge of the middle 
third. 


424. Calculation of Section.—Let ABDC, Fig. 91, be a section of 
a trapezoidal dam. Let the dimensions be as represented in the figure. 
Further, let w — weight of a unit volume of 
water, and w the weight of a unit volume of 
masonry. Let g = specific gravity of the masonry 

The components of the water-pressure 


— cf • * -A 


w 

w 


are P v and P h . 

For dams of this class there will usually be 
but two cases: first, when the front face BD is 
vertical or nearly so, and, second, when the back 


1 / 

/ 



\ j 

\ i 

0 1 I 

ry--*. 

• - 

G 

... 

A A 

a- • A— . « 






% 



Fig. 01. 


face AC is vertical, or is given a definite small 

batter. In the first case n is assumed and / or m is required; in the 











362 


MASONRY DAMS. 


second case m is given to find n or /. The problem is to find a value 
. of / such that the resultant of P and G will just cut the edge of the 
middle third. The bottom section will be the dangerous one, and the 
only case to be considered is for reservoir full. 

It is assumed for safety that the water rises to the top. 1 he value 

h h 

of P then equals wAC— ; its point of application is — above the base. 


The value of G can readily be expressed in terms of w' and thv dimen¬ 
sions, and its line of action found by rules of mechanics. 

We have then, briefly, 




wmh 




By dividing the moment about D of the several partial areas of the sec¬ 
tion by the total area, we find 


d = 


| n 2 a 2 ~\~ 2 an -J- \nP -f- am + mn 

a -f- l 


Equating now to zero the moments of P h , P v , and G about the outer 
edge of the middle third, we have, for stability, 



= o. 


Substituting in this equation the values of the forces given above, and 
the value of d , we get an expression containing /, in , and n\ but 
noting that / = a -f- m -f- ?i, we can eliminate either n or m. 


w 


We thus have for the case where n is given, putting — — g, 


l = sjn -(a+ n)\g - i) + #g + . (3) 

If the front face is vertical, n = o, and we have 

/ z=r Vh 2 — a 2 (g — i).(4) 

For the second case, having m given, we derive the expression 

l = VA + B 2 - B, . 


k? 


nr 


A. — a 2 —j— 2 am -I- - 4 — 

g g 


in which 


( 5 ) 










STABILITY OF HIGH DAMS. 


363 


and 




If the back face is vertical, 1/1 = 0, and we have 



If a = o, eq. (4) gives l = h, and eq. (6) l = It will thus 

yg 

give a more economical design to have the back face vertical or nearly 
so, rather than the front face. The latter form is, however, sometimes 
used for very low dams where designed as weirs, or where built in con¬ 
nection with such weirs. The front usually has then a batter of I to 2 
inches per foot, and the rear whatever is necessary to give stability. 

If the pressure on the base is desired, it can be found by the equa¬ 
tions of Art. 417, using for V a force equal to the resultant of G 
and P v . The force tending to slide the dam on the base is P h . The 
frictional resistance is V X coefficient of friction. If a section should 
be given and it is desired to investigate its stability, the value of the 
resultant pressure and its point of application can best be found by 
graphics. 

B. Stability of High Dams. 

425. General Statement of the Problem.—For dams exceeding 30 or 
40 feet in height, it is economy to build the lower face in the form of 
a curve or broken line. In designing a curved profile a certain height 
is soon reached, when it becomes necessary to investigate the stability 
of the dam for reservoir empty, and at a still greater elevation the con¬ 
dition that the stress shall not exceed a certain maximum value 
becomes the controlling factor. The design of the cross-section is there¬ 
fore a somewhat complicated problem, and it is impossible to represent 
by a formula a profile which will exactly fulfil all the conditions. 

Various formulas and methods of designing a profile have been pro¬ 
posed from time to time, differing more or less, but most of them based 
on the requirements for stability enumerated in Art. 419. Probably as 
simple a method as any is that adopted by Wegmann as the result of 
his studies for the Quaker Bridge Dam. The method is a general one 
and will be here briefly stated, and the working equations as derived 
by Wegmann will be given.* 

* For a full discussion of the subject see YVegmann’s “ Design and Constructioa 
of Dams/’ New York, 1890. 










3 6 4 


MASONR Y DAMS . 


426. Wegmann-s Method of Determining the Profile.—This method 
^consists in determining at successive horizontal sections, beginning at 
the top, the necessary width of section to fulfill the conditions stated in 
Art. 419, assuming the area enclosed between adjacent sections to be 
trapezoidal. In this way by taking the sections sufficiently close the 
profile may be determined with any desired degree of exactness. 

As it is necessary that a dam shall have a certain top width, a , the 
upper portion will consist of a rectangle until such a depth is reached 
as to bring the line of pressure with reservoir full at the outer edge of 
the middle third. Below this point the down-stream face will be 
battered and the other face will be continued vertically downwards until 
the resultant with reservoir empty just cuts the inner edge of the middle 
third. The inner face will then begin to receive a slight batter. 
Finally, a depth will be reached below which the length of the joint 
will be determined by the limiting pressures at the edges. 

The water is assumed to rise to the top of the dam in order to pro¬ 
vide for extreme conditions. Furthermore, at the lower sections of 
the dam, where the back face becomes slightly inclined, the vertical 
component of the water-pressure is neglected. The error arising 
therefrom is slight except in very high dams and where the allowable 
pressure is low, and is on the side of safety. 

427. The calculation of the profile is divided into five different stages, 
corresponding to the different sets of conditions to be met. 

First Stage .—Depth of rectangular portion. The depth at which 
the line of the resultant pressure will cut the edge of the middle third 

of a rectangle may be found by making l = a in 
equation (6), page 363, and solving for h\ we 
get 

h - aVg .(7) 

where h — height or depth, a — top width, and 
g — specific gravity of the masonry. 

Second Stage .—The back to be continued 
vertical and the front battered. The section 
from here down is determined by considering 
successive trapezoidal blocks. In Fig. 92 let 
CDFE be such a trapezoidal section of small 
thickness h situated immediately beneath the 
Fig * 92- portion ABDC already designed, which portion 

maybe of any form, but whose weight, area, etc., are known. The 
following notation will be used: 








STABILITY OF HIGH DAMS. 


3 6 5 


W weight of portion ABDC; 

G — weight of portion CDFE; 

W — resultant of W and G ; 

A = area of ABDC; 

A' = area of CDFE; 

m — distance of line of action of W from C; 
n — distance of line of action of W from E; 
l — length of joint CD; 
x — required length of joint EF; 
y — batter of CE; 
h — thickness of section; 

d ~ depth of water at E = height of dam above this point; 
p = limiting intensity of pressure at F; 

q — limiting intensity of pressure at E y usually greater than p\ 
w — weight of a cubic unit of water; 
w' = weight of a cubic unit of masonry; 

w r 

g =z specific gravity of masonry = —. 

The value of x y then, so long as CE can be made vertical, is given 
by the equation 

.( 8 > 


* = VB + C 2 — C, 


in which B 


d 3 + 6 4- z + /•. 


gh 


and: C — — 
2 


i (4 A 

IT 


+ 


The value of n is given by the equation 


h 


n = 


(x 2 + lx l 2 )-g -f- Am 
A + A' " 


( 9 ) 


x 


Equation (8) can be used so long as n is greater than 

In treating the next trapezoidal section the portion ABFE is now 
the known portion, the various properties of which are to be substituted 
for like properties of ABDC in the above equations. Thus the new 
value of in is n of eq. (9), etc. 

Third Stage .—For the next series of courses the face CE must be 

x 

battered so that n shall always be equal to The value of x is given 

J 

by the equation 

/ / / a \ 

• • ( io ) 










366 

and the value of y is 


MASONRY DAMS. 


2 A(x — 3 m) — hi 2 
y “ 6 A + h(2l + x) 



Fourth Stage .—When by the use of (io) and (n) the value of the 
pressure on the front face would exceed p, the formula is 



This value of x is to be used as soon as it becomes larger than the 

x 

value given by (io). The batter is still given by (ii); also, n = -• 

Fifth Stage .—When the pressure on the back face becomes equal 
to q } then the formula is . 

x =S/D-\-E*+E, .( 13)1 


in which D — — . 


d 3 


g P + q 


lh 

A + — 

2 

and E =- : -, and the batter is 


w 


- h 


P + i 


- h 


w 


y = 


A(px — 6 m) -j- lh{x — /) -j- x 1 - 


6 A + h( 2 l + x) 


• • • 


(H) 


Equation (13) is to be used when it gives a value of ;r greater than that 

qx^ 

found by eq. (12). For this case, 71 — \x — \ ' ffffZffl 7 )' 

The foregoing equations are all that are needed in designing the 
profile of any high dam. In'fact equations (12), (13), and (14) will 
not be used until a height of 100 feet or more is reached, depending 
upon the assumed values of p and q. 

Graphical methods of determining lines of pressures, and of check¬ 
ing the results found by algebraic processes, will readily suggest them¬ 
selves to the student. 

428. Effect of Approximations in the Foregoing Treatment.—The 

effect of neglecting the vertical component of the water-pressure on the 
inclined upper face is very small until the height becomes very great. 
Then this additional component acts to throw the resultant nearer the 
upper face and therefore to increase the pressures near this face and to 
decrease those near the lower face. In the last respect it tends to 
compensate for the error due to considering vertical forces only. The 
effect is greater the lower the allowable pressure intensities. 














STABILITY OF HIGH DAMS. 


367 




The effect of neglecting the inclination of the resultant pressure on 
any section is of course to derive a pressure less than the actual. To 
take account of this where the pressure determines the profile, the value 
of p in eqs. (12) and (13) may be reduced in the ratio of cos 2 a to 1, a 
being the inclination of the ‘resultant with the vertical. The value of 
p can thus be readily varied to accord with the change in a as the 
design proceeds. By making p constant and somewhat lower than q } 
as is done by Wegmann, the effect of inclined resultant can be approxi¬ 
mately allowed for. 

429. Use of a Standard Profile.—Fig. 93 represents Wegmann’s 
practical profile No. 2,” constructed for a dam 100 feet high without 
reference to pressures and with some /ST-*/# 
simplification of the theoretical out¬ 
line. The value assumed for g was 

corresponding to a weight of 20 - 
masonry of 145.8 pounds per cubic lo.'osjI 
foot. Such a section when once cal¬ 
culated can be used for any height of 
dam so long as the safe pressures are 
not exceeded, by simply cutting off a 
dam of the desired height from the 
standard section, or by changing all 
the dimensions proportionately, or by 
both processes, as may be necessary 
‘ to secure the required top width. If 
the safe pressures are exceeded, 'eqs. 

(12), (13), and (14) will have to be 
made use of for the lower sections. 


JO' 


I0\ 


50 


Mm 


70 


00 


J00' 


\ \ V 

yosowMS:jos7\ 

\ 

\ 

J3.53_ \ 

^ \ V 

I \ 

yj6o\H_05\./J6L'. 

\ \ 
-rtZJ-X./703_X 

\ 

_ JOM_ T__ /0J2__\ _20.25_. 

\ ^ 

I \ 

2207 \ 2M9 \ LOSS 


17.00 


66 . 7 / 

Fig. 93. 

If, for example, a profile is required for a dam 50 feet high and with 
8 feet top width, proceed as follows: Get by proportion, from Fig. 93, 
a profile with top width 8 feet and height 80 feet, and then use the 
upper 50 feet of such profile. For masonry with a different specific 
gravity a new standard profile would have to be calculated. 

The pressures at the various depths for the profile of Fig. 93 are 
given in Table No. 60, the data for which are from Wegmann. In 
dams of other heights but in which the dimensions are proportional, the 
pressures will also be proportional. Thus in a dam 120 feet high, 
made similar to Fig. 93 (top width 12 feet, bottom width = 66.11 X 


120 

100 


— 79.332 feet), the pressure at the bottom will be 7.16 X - 


120 


00 


8.92 tons. At a point 80 feet below the top the pressure will be pro- 













3 63 


MASONRY DAMS. 


8o 


portional to that given for the 100-foot dam at a point = X ioo = 


120 


66.7 feet from the top, - 4.9 x y^ = 5-88 tons per square foot. For 

a dam 150 feet high the maximum pressure is 7.16 X 1.5 — 10.74 t° ns 
per square foot. With safe values of 8 to 10 tons per square foot as 
commonly used it is seen that a standard profile such as here given 
would be suitable for dams up to about 150 feet in height. 

TABLE NO. 60 . 

PRESSURES FOR WEGMANN’s PRACTICAL PROFILE NO. 2. (FlG. 93.) 


Distance from 
Top of Dam in 
Feet. 

Pressures in Tons per Sq. Foot. 

Distance from 
Top of Dam in 
Feet. 

Pressures in Tons per Sq. Foot. 

Down-stream 

Face, 

Reservoir Full. 

Up-stream Face, 
Reservoir Empty 

Down-stream 

Face, 

Reservoir Full. 

Up-stream Face, 
Reservoir Empty 

9-372 

0-95 

0.68 

60 

4-45 

4-35 

15 

1.84 

I.69 

65 

4.78 

4-73 

20 

2.52 

1.77 

70 

5 -ii 

5 -n 

25.983 

2.77 

2.45 

75 

5-45 

5-48 

30 

2.80 

2.82 

80 

5-73 

5-86 

35 

2.97 

3-06 

85 

6.13 

6.22 

40 

3-23 

3-30 

90 

6.48 

6-59 

45 

3 - 51 , 

3-55 

95 

6.82 

6.96 

50 

3 - 8 i 

3 - 8 i 

100 

7.16 

7-33 

55 

4-13 

4.08 





430. Approximate Triangular Profile.—A profile very closely ap¬ 
proximating the type illustrated in Fig. 93 can be quickly determined 

from any assumed data as follows: Assume first the 
triangular profile ABC, Fig. 94, with vertical back 
face. For reservoir full the value of x is given by 
eq. (6), page 363, by putting a — o and replacing l 

d 

and h by x and d respectively. It is x — ■—=. 

\/ g 

This value is proportional to d and hence the line 
of pressure, reservoir full, cuts the outer edge of the 

-.ijC middle third at all sections. For reservoir empty 

Fig. 94. the resultant evidently cuts the inside edge of the 

middle third at all points, so that until a depth is 
reached where the allowable pressures are exceeded the triangle exactly 
satisfies the conditions of stability and is the most economical form. A 
zero top width is, however, impracticable, and to get a practical profile 
the block AFK of width a is added. The effect of this block is slightly 
to disturb the positions of the pressure lines, but for high dams the 






























STABILITY OB HIGH DAMS. 


369 


variation is so small as to be negligible. The line of pressure, reser¬ 
voir full, is brought slightly within the middle third, while that for 
reservoir empty passes a very little outside. Such a profile, rounded 
off slightly at the point K, can therefore be used with practical exact¬ 
ness for dams of such height that the pressures need not be considered. 
If more exact methods are desired, this form may be used for preliminary 
plans. It also affords a ready check on more elaborate determinations. 

The maximum pressure intensity, /, of the triangular profile is 

1 2G 

equal to —- = w'd. For a value of w — 145.8 and d = 150, p = 

10.93 tons per square foot as compared to 10.74 tons for the profile of 
Fig- 93- "I he coefficient of friction necessary for stability against slid- 

P 1 

ing is equal to = —7=- — .65 for a value of g — 2\. 

Lr ^/ g 

431. Forces not Considered in the Preceding Analysis.—As already 
remarked, the upward pressure of the water is usually neglected. In 
one dam built recently, the Gileppe Dam, 154 feet high, this action 
was allowed for, resulting in a greatly increased section; but the con¬ 
tinued stability of many high dams in which this element is neglected 
indicates that it need not be taken into account. 

It has been shown that with good mortar joints and good connec¬ 
tion with bed-rock the uplift cannot possibly be more than a few pounds 
per cubic foot. For small areas near crevices where springs occur it 
might be very considerable, but such areas would in any case be but a 
small fraction of the whole. A system of drains such as used in the 
Vyrnwy Dam, page 385, would avoid all possibility of such action 
beyond that due to the head of water on the lower face. A dam 
founded on a loose porous foundation would of course be differently 
conditioned, but such would scarcely be a masonry dam. 

There is usually a certain depth of water on the lower face. The 
pressure of this should be taken into account when this part of the 
section is reached ; also any considerable unbalanced earth-pressure. 

Wind-pressure, reservoir empty, will add slightly to the stresses, 
but the amount is not sufficient to be considered. Wave action will 
add something to the pressure of the water, but this may be considered 
as amply provided for in assuming the water-level at the top of the 
dam. 

The pressure of ice is sometimes very great, but what allowance 
should be made for this is impossible to say. The maximum pressure 
would be measured by the crushing strength of ice, which may be taken 
at about 400 pounds per square inch. Such great pressures would 




370 


MASON AY BAMS. 



doubtless seldom occur, but may be approached in confined locations 
for either a high or a low dam.* The pressures due to ice moved by 
die wind in the spring would be very much less and would correspond 
to a strength of ice of probably not over 30 or 40 pounds per square 
inch, perhaps 4000 or 5000 pounds per lineal foot for ordinary cases. 
In the case of the Quaker Bridge Dam it was the opinion of the 
board of experts that ice-pressure should be taken at 43,000 pounds 
per lineal foot. The effect of such a force can be taken account of by 
combining it with the horizontal pressure of the water.' Usually a suffi¬ 
cient margin of strength to resist ice-pressure will be afforded by the 
mass of masonry above high-water line dimensioned according to 
empirical rules of practice. 

432. Top Width and Height above Water-line.—If the dam is to be 

used as a driveway, the top width will have to be at least 8 feet besides 
width of parapets. Otherwise the width and height above high-water 
line must be such as to secure stability against wave and ice action as 
just noted, and to prevent waves from washing over the top. A formula 
for height of waves was given in the previous chapter (page 334). In 
practice the width varies from a minimum of 4 to 5 feet for low dams 
to 1 5 or 20 feet for very high dams; and the height above high-water 
line from 2 or 3 feet to about 10 feet. In some cases much larger 
dimensions may be required for low dams than those given. 

433. Curved Dams. —Arch Action alone Considered .—Up to this 
point it has been assumed that a dam resists overturning by gravity 
action alone. Obviously if a short dam be built with a sharp curvature 
convex up-stream, with its flanks resting against rigid supports, over¬ 
turning will also be resisted by arch action. In investigating the 
stresses of such a dam it may be looked upon as a section of a circular 
open well constructed in the middle of a reservoir. Omitting any 
resistance by gravity action and assuming each horizontal lamina to 
support the water-pressure against itself independently of the others, 
the horizontal compressive stress in a lamina 1 foot thick will be equal 
to wdr , where w — weight of water, d = depth of lamina below water- 
surface, and r — radius of curvature of the dam. If this pressure be 
assumed as uniformly distributed over the cross-section of the iamina, 

wdr 

the pressure per square foot will then be equal to / — -, where t 


thickness of wall at the depth d. For a constant value of / the thick- 


* For account of failure of a dam at Minneapolis by ice-pressure, see Eng. News, 
1899, xli. p. 307. 





STABILITY OF HIGH DAMS. 


371 


ness t should vary with d, thus giving a triangular profile in which 

wdr . 62. ^dr 

t — ——. taking p — 10 tons = 20,000 pounds, we have t — - 

p r 20,000 

= .0031 dr. The value of t for a gravity dam with triangular profile 

was shown to be equal to —Putting^ = 2-J, this becomes t — .66d< 

\/ g 

Theoretically, therefore, the two sections would be equal when r — 

,66 

— = 213 feet. This rough calculation indicates that the only 
.0031 & J 


situation where a purely arch type can be economically considered is 
in a very narrow valley. 

434. Gravity and Arch Action. —A curved dam with its base 
securely fastened to the foundation cannot wholly fail to resist by 
gravity. A gravity dam may be looked upon as a vertical cantilever 
beam which when loaded will deflect until certain internal stresses are 
developed sufficient to resist the load. (The vertical force of gravity 
produces a longitudinal compression in this beam and prevents any of 
the stresses from becoming tensile.) If such a dam be now curved in 
plan, the downward deflection of the top will also be resisted by the 
circumferential stresses or arch action. The relative amounts of beam 
and arch action will be proportional to the rigidity of the two paths 
over which the load passes. Thus a massive dam of long radius would 
be very much more rigid as a beam than as an arch, and the arch 
action would therefore be very small. On the other hand a thin wall 
of short radius would be, especially towards the top, of relatively great 
flexibility as a beam, and such would be mostly supported by arch 
action. No curved dam will therefore resist wholly by arch action, 
nor by gravity or beam action. 

1^ would theoretically be possible, by taking account of both 
actions, to design a curved dam section that would be less in area than 
cither the gravity or the arch dam. Plowever, the variation in length 
of dam from top to bottom, the variation in thickness and in the elas¬ 
ticity in different directions due to differences in compactness, are some 
of the elements that make the problem too uncertain and complicated 
to admit of this being practically done. 

435. Methods Followed in Practice. —In practice there are three 
methods followed : (1) to make the dam straight and therefore a gravity 
dam; (2) to give the dam a sharp curvature when conditions will per¬ 
mit, and rely more or less on arch action; and (3) to build a gravity 
dam in a curve, and consider any arch action as an additional element 






372 


MASONRY RAMS. 


of safety. In the case of moderately short dams the third method is 
considered preferable by most engineers. For long dams, however, 
the advantage gained by using a curved plan of long radius would be 
very slight and not commensurate with the extra trouble and expense 
involved. For very short dams where radii of 200 or 300 feet can be 
used the second method may be employed. It is to be noted that in 
the bottom of a narrow valley where the thickness of a gravity dam is 
perhaps greater than its length, arch action may take place even in a 
straight dam. 

436. Exaviples .—A few dams have been built in which the section is 
materially less than that required for gravity. The boldest of these is the 
Bear Valley Dam of California, illustrated in Fig. 95. The radius of the top 
is about 250 feet. It is built of uncoursed rubble. If it be assumed to act 
as a gravity dam, the resultant pressure would pass many feet outside the base. 
Calculated as an arch dam the pressures near the base are 40 tons or more 
per square foot. Another dam of this type is the Zola dam in France. It is 
123 feet high and 41.8 feet thick at the base and has a radius of curvature of 
158 feet. 




The Sweetwater dam of California may also be considered of this type 
although designed as a gravity dam (Fig. 96). Assumed as such, the line of 
pressure falls at about the middle of the outside third. It has a radius of 
curvature of 222 feet and undoubtedly acts partly as an arch. In 1895 it was 
overtopped for 40 hours by a high flood without injury, the water standing 
22 inches above the parapet. It is built of uncoursed rubble, great care 
having been taken in executing the work. The masonry weighs about 164 
pounds per cubic foot.* 


* Trans. Am. Soc. C. E., 1888, xix. p. 201. 


























COATS TR UCTION. 


373 


CONSTRUCTION. 

437. The Foundation.—For large dams the foundation should be 
solid rock. In preparing the foundation surface all loose and partially 
decomposed material should be excavated until a firm base is reached. 
If the bottom is smooth it should be roughened by excavating shallow 
cavities in the rock. At points where crevices occur the excavation 
must be carried down to a solid bottom and all loose material must be 
removed. After an acceptable surface is reached it should be 
thoroughly washed or scrubbed with water in order that there may be 
a secure bond between the foundation and the masonry. Many 
engineers follow the practice of coating the prepared foundation with a 
layer of neat cement. The great care necessary in this part of the 
work is illustrated by the following specification relating to the con¬ 
struction of the concrete dam at Butte, Mont., Chester B. Davis, Mem. 
Am. Soc. C. E., engineer: 

“ Whenever the slope of the solid bed-rock of the dam-site makes 
a greater angle than 5 0 with the horizontal it must be rough-stepped 
by removing the least amount possible of bed-rock. Where the rock 
beneath the dam is smooth and free from cross-seams it must be made 
rough either by stepping or blasting holes with a superficial area of from 
6 to 12 feet and a depth of from 1 to 3 feet. 

“Each square foot of the natural bed-rock beneath the proposed 
structure, and to include an area to an elevation of 20 feet above the 
flow-line, and for at least 200 feet above and 100 feet below the upper 
and lower toes of the dam, must be carefully examined and everything 
not natural, true, and perfectly solid granite rock over this area be 
removed. 

“Each crevice, joint, or other opening beneath the structure must 
be examined and tested and all material removed which would be 
started or stirred by a pressure up to at least the maximum load on the 
base or abutments, or by a minimum strain of 25 tons per square foot. 
Each crevice, joint, crack, or other opening must be filled with granite 
or concrete after completing the blasting for the portion of the dam 
where located. Openings outside the limits of the structure must be 
filled flush with the surface and rammed where possible until perfectly 
compact. Openings beneath the dam must be treated in the same 
manner, unless large enough to be properly filled with the concrete 
used for the base of the dam. In all cases these openings must first 
be grouted. ’ ’ * 


* Eng. News , 1892, xxvm. p. 554. 




374 


MASONRY DAMS . 


In building large dams the excavation for the foundation becomes 
a matter of considerable difficulty, especially where a great depth of 
earth overlies the rock. The excavation in such a case becomes very 
broad, and as a consequence is usually made with such slopes as to be 
self-supporting, no attempt being made to use bracing. Ample pump¬ 
ing capacity is here a prime requisite. At the New Croton Dam the 
foundation was 1300 by 500 feet by 130 feet deep. The stream was 
diverted by means of a temporary channel and large wing dams con¬ 
structed above and below the excavation. 

438. Earth Foundations .—Low dams of masonry are quite often 
founded on hard clay or even compact sand, a construction often made 
necessary where waste-weirs are placed in earthen embankments. In 
building upon such foundations great care must be observed to avoid 
overloading the material and to prevent seepage under the dam. Plank 
foundations are very commonly used to aid in distributing the load, 
and sheet-piling driven well into the foundation at the upper edge of the 
dam is of great value in reducing seepage. 

A good example of a dam built on earth foundation is the one at 
Southington, Conn., shown in Fig. 97. In the construction of this 



Fig. 97.— Southington Dam. 

dam the bed of the stream, which was a very fine quicksand, was pre¬ 
pared by excavating two trenches parallel to the face of the dam and 
of a depth of about 3 feet. Sills were laid at the bottom and the top 
of the excavation, and sheet-piling driven and spiked to them. The 
trenches were then filled with concrete and the entire foundation 
covered with a layer of concrete 1 foot thick by 1 5 feet wide. The 
dam is built of granite rubble.* (See also description of Dunning’s 
Dam, page 383.) 


* Trans. Am. Soc. C. E., 1S86, xv. p. 887. 














































CONSTRUCTION . 


375 


439. Percolation of Water beneath the Dam .—It is quite frequentlv 
the case that considerable trouble is experienced from water seeping 
through at the foundation surface and appearing in the form of large 
or small springs. In handling these springs the same general methods 
?re used as described for earthen dams. Great care must be taken to 
avoid water-pressure existing over any considerable area of the bottom 
of the dam, as such pressure is usually assumed not to exist. The 
great importance of this matter is apparent when we consider the 
excessive section used in the Gileppe Dam where full water-pressure 
was provided for. The failure of the Bouzey Dam is attributed to water 
getting into cracks caused by tension in the masonry due to a too 
narrow section. 

If the water is present in large quantities, the most certain way of 
avoiding upward pressure is to lead the water out to the lower face of 
the dam, as was done for the Vyrnwy Dam. A French engineer^ 
Maurice Levy, has suggested the construction of a guard-wall in front 
of the dam and connected therewith by means of short buttresses. By 
this arrangement any water percolating through the wall could be 
readily drained out from the spaces between wall and dam. Percola¬ 
tion and resulting pressures are to some extent avoided by making the 
dam itself as impervious as possible, and also the foundation for some 
distance above the upper face of the dam.* 

In preparing the foundation of the New Croton Dam the greatest 
care was exercised in removing all unsound material and in building 
over springs of water in such a way as to avoid as far as possible all 
upward pressure. The rock foundation was carefully scrubbed and all 
erosions and cracks were traced out by drilling numerous holes in their 
vicinity. Such cracks were usually piped and filled with grout forced 
in under pressure. Where a flow of water was encountered pipes were 
also led to an adjacent drain or sump and the water permitted to escape 
until the masonry had been built up for some distance. The pipes 
were then filled with grout. For a detailed description of this impor¬ 
tant work, see paper by C. S. Gowan in Trans. Am. Soc. C. E., 1900, 
XLIII. page 469. 

440. Construction of the Masonry.—Uncoursed rubble or concrete 
is usually employed in dam construction. The object to be attained 
is to secure a homogeneous structure, free from all through joints or 
weak places of separation. Concrete, well placed, is in this respect 
an ideal material. Rubble masonry, in which all joints are thoroughly 


* Mr. Freeman in his report on New York’s Water-supply suggests the use of a 
thin sheet of lead placed vertically in the masonry a few feet back of the face. 




3 7 6 


MASONRY DAMS. 


filled with mortar, and larger spaces with concrete, has been used foi 
most of the high dams. It is in fact a rubble concrete where the 
mortar is reduced to as small a proportion as possible. The material 
to be adopted in any case will be determined largely by the question 
of expense. 

Rubble is often faced with broken-range ashlar. This adds strength 
to the face, but is objected to on the ground of its greater rigidity and 
therefore its tendency in settling to separate from the rubble backing. 
Such facing should be well bonded to the body of the structure. 
Several recent important dams, among which are the Nashua Dam and 
the New Croton Dam, have ashlar facing. In the Croton Dam the 
facing courses vary in size from 30 to 15 inches. The joints are not to 
exceed i inch for 4 inches from the face. In each course every third 
stone is to be a header, with a length of at least 4 feet. The stretchers 
are to be not less than 3 feet wide and not more than 7 feet long.* 

Beds are as a rule made horizontal, except in the facing, but in 
the Remsheid Dam, completed in 1891, the joints were made to vary 

somewhat according to the line of pressure 
as shown in Fig. 98. Greater resistance 
against shearing is thus obtained. 

Cement mortar should be made in such 
proportions as to be practically impervious, 
particularly near the up-stream face. Port¬ 
land or Rosendale cement mortar 2 to 1, 
or Portland 3 to 1, is usually employed, 
but the last is not entirely impervious. 
It is desirable to use the stronger mortar 
where the heavier stresses exist and also 
near the faces. 

The size of stone to be used in rubble 
masonry depends chiefly on the matter of 
convenience. In some of the modern 
dams stones measuring 6 to 8 cubic yards have been used. Large 
spaces are left between these which are filled with cement or with 
smaller stones and mortar. 

In constructing the masonry the principal points to be emphasized 
are clean surfaces, irregular surfaces, joints absolutely filled with com¬ 
pact mortar, no grouting, great care to give good bedding, and con¬ 
stant supervision. Mortar and cement should be thoroughly rammed 
into all spaces, using for this purpose suitable forms of rammers. 



Fig. 98. —The Remsheid Dam. 


* Wegmann. The Water-supply of New York, p. 207. 

















EARTH BACKING FOR MASONRY BAMS. 


377 


Concrete to be practically impervious should not usually have a 
greater proportion of sand and stone than that given by the mixture of 
1:3:5. Larger proportions of stone have been used, however, with 
good results, such as 1 : 31 : The greater the proportion of stone 

the better, as long as all voids are filled, but with high ratios of stone 
greater care is required in the manipulation. Close supervision in the 
mixing and laying is very necessary to secure a good concrete. 

The water of streams is cared for during construction by methods 
similar to those described in the preceding chapter (page 352). 

441. Imperviousness.—Imperviousness is very difficult to secure, 
and in fact most masonry dams leak slightly. That it can be practically 
obtained is, however, shown by the results reported in the case of 
several of the modern dams. The result in this respect depends chiefly 
upon the care taken in executing the work. Special precautions may, 
however, be used to good advantage, such as the use of a more im¬ 
pervious mortar near the up-stream face of the dam, or the plastering 
of the upper face with neat or i-to-i cement mortar. In the Remsheid 
Dam a continuous joint of asphalt was used just back of the face-stones 
and on the foundation surface for a short distance above the dam. 

Whether cracks will necessarily form in dams is a disputed point. 
In some they have occurred and in some apparently not. In long nar¬ 
row walls cracks are very sure to form, due to temperature changes, 
but in the massive walls of dams the changes in the interior are very 
slight, and it is undoubtedly true that in some of the modern dams 
at least, no cracking of the interior has occurred. In the Vyrnwy Dam 
the effect of temperature changes has been measured at a height of 80 
feet. A maximum movement of 0.366 mm. due to variations in 
temperature from day to night has been noted.t In the Remsheid 
Dam, curved at 410 feet radius and 82 feet high, a movement of the 
crest of inches, due to filling of the reservoir, and of -§• inch, due 
to temperature changes, has been observed. The curved form was 
here considered to have prevented cracking. J 

442. Earth Backing for Masonry Dams.—In the construction of 
dams of moderate height, earth backing is often carried up to the 
water-level with a slope of 2 or 3 to 1, as in an earthen dam. Such a 
backing, if more porous than the dam, will not reduce the pressure 


* See description of Indian River Dam in Eng. News, 1899, xli. p. 310 ; also a 
paper by G. W. Rafter on the Theory of Concrete in Trans. Am. Soc. C. E., 1899, 
xlii. p. 104. 

+ Proc. Inst. C. E., cxv. p. 117. 

X Eng. News, 1896, xxxv. p. 76. 



378 


MASONRY BAMS. 


against the wall, but will rather increase it and is ordinarily of doubtful 
advantage. If, however, a dam is located on a porous or bad founda¬ 
tion or on one of earth, a good, compact backing will much reduce the 
percolation under the dam, and therefore the tendency of any upward 
pressure, and will add considerably to the safety of the structure. It is 
especially applicable to spillways in earthen embankments. The earth 
backing in that case acts also as a protection for the back of the 
masonry against injury from ice and driftwood. (See Figs. 97 and 
104.) 




Section through Gate-house. 


-EI.2U.0Z 


EI.Z26./4 


Section through Waste-weir. 


k» J 


a 

o 

h 

c 


Paving 


Rectangular Coping 

k -x_: 

Stripped Ledge'' 


! 

oc 

1 A/fill _- 

1 

1111 

!j%* 

-1 



jjj 

PavinqpS\ 

mrp^j 




onrr 



- bottom of Core Wall 

- 1 Op •• ff * 

y Rubble Tongue 


6rassed Slope 
Bundat/o # 

"-■^dSUUr// 



Plan of Gate-house and Wing Wall. 

Fig. 99.—Dam No. 5, Boston Water-works. 

(From Engineering News , vol. xxxm.) 


443. Draw-off Arrangements,—The arrangements for drawing water 
from the reservoir are similar in general to those described in the last 
chapter. The outlet-pipes are built in the masonry at or near the 
lowest point of the dam, and terminate in a gate-chamber constructed 
just above and in connection with the dam. d he gate-chamber has 


























































































DRA W-OFF ARRANGEMENTS. 


379 


the same functions as explained in the case of earthen embankments. 
No danger is here to be apprehended from constructing the pipes in the 
body of the dam. 

An outlet arrangement of common form is shown in Fig. 99, which 
illustrates details of Dam No. 5 of the Boston Metropolitan Water¬ 
works. The figure shows the weir, gate-house, and wing walls al? the 
junction of the earth embankment and masonry dam. The gate-cham¬ 
ber is very similar to those used in several of the dams of the New 
York Water-works. (For section of the earth embankment, see Fig. 
74. page 332.) 

Simpler arrangements than the above may often be adopted to 
advantage. Thus if screening is not required, a single chamber answers 
every purpose. Even this is dispensed with in some cases, as for 
example, in the construction of the large dam at Butte, Mont., and 


Fig. 


0 



Sectional 

Elevation. 



Half Plan of Second 
and Third Rings. 



Sectional Plan 
of Bellmouth. 


100.—Cover-valves, Plymouth Reservoir, England. 

(From Engineering News , vol. xlii.) 


more recently in the dam at Plymouth, England. In these cases the 
outlet-pipes pass through the dam and terminate in short vertical pipes 
just above the upper face. Cover-valves are fitted over the ends of 
these pipes and are operated by chains from windlasses above. Details 
of the valves used at Plymouth are illustrated in Fig. 100. As shown 
in the sectional elevation, the valve is made in three sections which are 
successively raised when the valve is opened. This form of construc¬ 
tion is best suited to the case where the valves need not be often 
operated. In the winter the ice would have to be kept cut away from 
around the chains or pipes. 

Where a dam is built across a narrow valley a scouring-sluice or 












380 


MASONRY DAMS. 


large waste-pipe placed at the lowest point will enable much of the silt 
deposit to be removed by flushing. These deposits may be prevented 
to some extent by building small barricades or dams at the entrance 
of the various streams into the reservoir, thus forming small settling- 
basins which may be more readily cleaned than the large reservoir. 
Flopd-channels are also sometimes constructed in the case of small 
streams which are used to lead flood-waters that are not needed around 
the end of the dam and thus prevent to some extent the accumulation 
of sediment. 

444, Masonry Waste-weirs.—Masonry dams are not usually designed 
to allow water to pass over their entire length, but a certain portion 
only is made to act as a waste-weir. As was the case with earthen 
dams, the waste-weir is often located at the extreme end of the dam, 
the overflow passing down a prepared channel in the hillside. Whether 
it is so placed, or located more nearly in the axis of the valley, depends 
chiefly upon the topography and nature of the foundations. 

The form of a masonry weir depends much upon local conditions, 
chief of which are height of dam, character of foundation, amount of 
ice and driftwood to be expected, and quantity of water to be provided 
for. A weir is essentially a dam with its top and lower face so con¬ 
structed as to permit the water to pass over it without damage. Besides 
the design of the profile, the protection of the stream-bed below the 
dam is a very important feature, as many dams have been undermined 
by failure at this point even where the bed has been solid rock. 

With respect to the form of construction, masonry weirs may be 
divided into three classes: (1) weirs with a nearly vertical front face, 
allowing a free fall to the water; (2) weirs with a curved lower face; 
(3) weirs with a stepped lower face. 

445 * (0 W&rs Allowing Free Fall .—These are ordinarily used for 
low falls of 10 to 20 feet, depending on the character of the bottom. 
The front face is made at a batter of 1 to 2 inches per foot, and the rear 
face whatever is necessary to secure stability. The top width is made 
sufficient to resist the impact of ice, logs, etc., 5 to 8 feet usually being 
sufficient. The cap stones should incline downwards up-stream, to 
relieve them from blows on the back edge. They must be large and 
well laid, and, where subject to severe shocks, well doweled and 
clamped together. It may also be necessary to anchor the masonry to 
the bed-rock. With earth foundations, an earth backing, finished with 
gravel or paving, is often carried up flush with the back edge. The 
advantage of this has been noted in Art. 442. 

If the stream-bed is not solid rock, it must be well protected by an 





MASONRY WASTE WEIRS. 


3 »I 


apron of timber or stone, the former being quite temporary unless con¬ 
stantly wet. A timber apron is usually made as a continuation of the 
foundation platform with additional layers of thick planking. A stone 
apron varies in construction according to the requirements from a mere 
paving, to a heavy apron of broken stone, concrete, and one or more 
layers of heavy paving set in cement. 

With falls greater than 10 or 20 feet, aprons alone are not sufficient 
security against scour, and even with rock bottom the wear becomes too 
great, especially if large quantities of ice and logs pass over the weir. 
Free falls for greater heights may still be used by protecting the bed 
by means of a water-cushion, formed by a subsidiary weir built a short 
distance below the main weir. This reduces the height of fall and also 
forms a pond into which the water falls and which absorbs its energy. 
The depth of such a water-cushion depends on the mass of water and 
character of the bed. It is frequently made one-fifth or one-fourth the 
height of the main weir. 

An example of a weir of considerable height having a free fall is the 
Macoupin Intake Dam of the East Jersey 
Water Company, illustrated in Fig. 101, 

Clemens Herschel, Mem. Am. Soc. C. E., 
engineer. The coping-stones are well 
doweled together and bolted to the body 
of the dam. The stream-bed is solid rock. 

(See also Fig. 97, page 374.) 

446. (2) Weirs with a Curved 
Lower Face. —The object of this form 
is to guide the water smoothly over 
the dam, and at the bottom to deliver 
it tangentially with respect to the 
stream-bed. In this way the water 
arrives at the bottom with nearly the 
same velocity as with a free fall but 
with changed direction, a great advantage where logs and ice pass over 
the dam. The scouring effect is, however, very great, and in high 
weirs a water-cushion is here also necessary where large volumes aie 
dealt with. If the depth of water is slight, the velocity may be reduced 
by leaving the surface of the weir very rough, as in the Vyrnwy Dam. 
For high weirs the section is designed as for a high dam (making due 
allowance for the extra pressure due to the superelevation of the water- 
surface, and for shocks, etc.), and then rounded off. The rear face is 
made nearly vertical, as in high dams. 












382 


MASONRY DAMS. 


The convex top curve to be given to a dam should be full enough 
to prevent the water leaving-the surface. This will be given by the 
parabolic curve which the water would take in a free fall with the 
initial horizontal velocity corresponding to the depth on the weir. 
According to the formula for weirs, the average velocity of the water 
is v — c.\\ 2 gH. (See page 219.) In time t the abscissa of the 


parabola is x = vt, and the ordinate is y — \gt 2 , whence y — -^;tr 2 is 

the equation of the parabola. In a long weir with ends not freely 
exposed to the entrance of air the normal pressure is not maintained 
under a sheet of water, and it will be forced by the exterior pressure to 
follow a sharper curve than the parabola above. Such action is very 
observable in many weirs. 


£/ GO 



Fig. 102.—Colorado River Dam at Austin, Texas. 

A noteworthy example of a large dam made to act as a weir is the dam 
across the Colorado River at Austin, 1 exas, built for water-power purposes 
(Fig. 102). This structure is 1275 feet long and is built of rubble with 
granite facing. It was designed to pass flood-waters to a depth of about 15 
feet on the crest, but on April 7, 1900, during a flood in which the depth of 
water flowing was about 11 feet, a large section of the dam failed, a portion 
sliding down-stream and remaining upright, while a portion was broken up and 
washed away. The cause of the failure is not definitely known, but some 
weakening of the foundation is evident, due either to erosion by percolation 
or by the water falling below the dam.* This dam is an exception in respect 
to its height and the great volume of water to be provided for, and the protec¬ 
tion of the stream-bed from the action of the great mass of water is in such a 
case a matter of very great importance. 

Tig. 103 illustrates another dam built for power purposes and designed 
for a large flow. The facing of this dam is also of granite, the curve for the 


* See Eng . News , April 12, 1900, et seq.\ Eng . Record , April 14, 1900, et seq . 


















WASTE WE ITS. 


383 

upper portion being a parabola corresponding to the curve of the flowing 
water when 4 feet deep. The stones are thoroughly doweled together. The 
lower portion of the dam is cycloidal, and the upward slope of the toe is intro¬ 
duced so as to form somewhat of a water-cushion.* 

447 * ( 3 ) Weirs with a Stepped Profile. —In this form the lower face 
is stepped instead of curved, with the object of breaking the fall into 
several small steps and absorbing the energy of the water before it 
reaches the bottom. This very much simplifies the problem of scour, 



Fig. 103.—The New Holyoke Dam across the Connecticut River. 

and at the same time gives a form cheaper to construct than the curved 
outline. It is well suited to carry moderate quantities of water. With 
the stepped profile the wear comes more on the dam, while with the 
curved form it is more on the stream-bed. The masonry of the steps 
requires to be of the heaviest and most substantial character. Single 
stones should be used extending well under the masonry above. 

An example of a spillway of considerable height is shown in Fig. 104, a 
section of the Dunning’s Dam, E. Sherman Gould, Mem. Am. Soc. C. E., 



engineer. The dam is noteworthy as being partly founded on rock and partly 
on earth, conditions very difficult to deal with. The weir is founded on clay 
and fine sand. The apron consists of, first, a filling of large stones, then one 
foot of concrete, then a heavy paving in cement mortar. Below is a timber 
crib filled with stones, and farther down, the channel is riprapped. The dam 


* Eng. News, 1897, xxxvn. p. 292. 


































3^4 


MASONRY DAMS. 


is backed with earth, which is considered by the designer as being a valuable 
safeguard for a masonry dam.* 

Fig. 105 is a section through the highest portion of the spillway of the 


Fig. 105.—Spillway, New Croton Dam. 



New Croton Dam. This design may be considered as well representing 
modern practice in this direction. 



448. Other Examples of Dams.—An example of a recently constructed 
masonry dam of small dimensions is illustrated in Fig. 106. The front face 


* Trans. Am. Soc. C. E., 1894, xxxn. p. 737. 









































EXAMPLES OF MASONRY DAMS. 


335 


is vertical throughout, and at the centre is a spillway 40 feet long and 21 
inches below the top of the dam. Earth backing extends to within 7 feet of 
the top. The foundation here was hard-pan at a depth of about 3^ feet 
below the surface.* 

Fig. 107 illustrates a small modern dam across Indian River, N. Y., 
in the upper Hudson valley, built for water-power and navigation purposes. 
The dam is of rubble masonry with spaces filled with concrete, f 

On page 386 are illustrated the sections of several of the largest dams of 
the world, all sections being drawn to the same scale. Of these dams the New 
Croton will, when completed, be the largest. This dam consists of a masonry 
portion, of the section shown, for a length of about 700 feet, a curved masonry 
spillway at one end 1000 feet long (Fig. 105), and at the other end an earthen 
embankment with masonry core-wall (Fig. 75, page 333). The masonry dam 
has a maximum height above foundation of about 290 feet, measuring to the 
deepest pocket. In section it is practically the same as adopted for the 
Quaker Bridge Dam. The height of spillway varies from 10 to 150 feet. 
Rubble masonry is used for hearting, and ashlar for facing. The steps on the 
waste-weir are to be made of block masonry, and of sufficient depth to bond 
under the step above. The estimated cost of this dam is nearly $5,000,000. 
It was begun in 1892, and will be completed about 1903. 

The Vyrnwy dam, which is a part of the Liverpool Water-works, is note¬ 
worthy on account of the great care taken to obtain strong, impervious 
masonry, and in the provision made for drainage. It is built of large rubble 
masonry, a large proportion of the blocks ranging from 2 to 8 tons in weight. 
All stones were washed and scrubbed with jets of water under 140 feet 
pressure. The mortar was made of Portland cement 1 to 2 and 1 to 2 \, the 
sand being composed of pulverized rock mixed with natural sand. Large 
stones were bedded upon a 2-inch layer of mortar which was first beaten to 
expel the air. The stones were also beaten into place by blows from hand- 
mauls. The spaces between the stones were filled with small rubble or concrete 
rammed into place. The crushing strength of the concrete, one year old, 
was about 187 tons per square foot. The specific gravity of the masonry was 
found to be about 2.5. ilie maximum pressure at the upper face is 8.7 tons 
t and at the lower face 6.36 tons per square foot. To prevent the existence 
of hydrostatic pressure in the dam a system of drains was constructed in the 
foundation. These drains are 9 to 12 inches square and are kept 25 feet from 
the front face. They connect with a concrete tunnel 4 feet by 2 feet 6 inches 
wide running longitudinally through the dam and 46^- feet above the base. 
This opens out to the surface by a cross-tunnel. Length of dam = 1350 feet. 
Maximum height — 136 feet. It is designed to act as a waste-weir. J 

The San Mateo Dam in California is noteworthy as having been built 
entirely of concrete blocks, each of about 9 tons weight. 

The Furens Dam, France, is famous as being the first one constructed on 
scientific principles, and until recently the highest dam in existence. It was 
completed in 1866. 

The Periar Dam, Madras, is another notable concrete dam. The maxi¬ 
mum pressure intensity is stated to be 8 tons per square foot. 


* Eng. Record , 1898, XXXVIII. p. 559. 
f Eng. News , 1899, XLI. p. 310. 

% Proc. Inst. C. E., cxxvi. p. 24. 



386 


MASONRY DAMS. 



Vyrnwy 

Fig. 108.—Profiles of some High Masonry Dams. 


- J rt. , 60 '- -- T- . / 70-6 



































LITER A TURK. 


3 3/ 


449. Cost.—The cost of constructing masonry dams will vary 
greatly with the local conditions. If these are reasonably favorable as 
to transportation and ease of securing stone, the range of prices for the 
principal items will be about as follows: Earth excavation 25 to 50 
cents per cubic yard; rock excavation $1.00 to $2.00; rubble masonry, 
natural cement, $3-5° t° $5- 00 > concrete masonry, natural cement, 
$ 3 - 5 ° to $5-°o; for masonry laid in Portland cement add $1.00 to 
$1.5° per cubic yard; rock-faced ashlar masonry $10.00 to $15.00; 
dimension-stone masonry for gate-houses, etc., $15.00 to $30.00; 
paving $2.00 to $3.00; riprap $1.50 to $2.00. 

The prices per cubic yard for two of the large masonry dams of the 
New York City Water-works and for the Dunning’s Dam, Scranton, 
Pa., were as follows: 


Earth excavation. 

Titicus 

Dam. 

New Croton 
Dam. 

$ .61 

t nc 

Dunning’s 

Dam. 

$ -35 

Rock excavation. 


Rubble masonry (natural cement). 

Concrete masonry (natural cement). 

Brick masonry (natural cement). 

Granite dimension stone. 


4.05 * 

4-55 

• • • • 

a ^ 00 

6.25 * 
5*oo 

11.00 

Paving. 

Riprap. 

Cut stone. 


2.50 

i -75 

• • • • 

1.50 

11.00 

The high price for excavation for the Croton Dam is due to the very 
great size and depth of the pit. The contract price for 60,000 cubic 
yards of rubble masonry for the Austin Dam was $3.60 per cubic yard 


for natural cement and $6.10 for Portland. The price for granite facing 
was from. $11.00 to $15.00. 

In localities remote from railroads and where suitable stone cannot 
readily be obtained the cost may be several times the above figures. 
For a more detailed analysis of the cost of masonry see Baker’s 
“ Masonry Construction. 

LITERATURE. 

1. Krantz. A Study on Reservoir Walls. New York, 1883. 

2. Wilson. Manual of Irrigation Engineering. New York, 1893. 

3. Wegmann. Design and Construction of Dams. New York, 1899. 

4. Coventry. The Design and Stability of Masonry Dams. Proc. Inst. 

C. E., 1885-86, lxxxv. p. 281. 

5. Grugnola. The Gileppe Dam, near Verviers, Belgium. Eng. News, 

1886, xvi. p. 418. 

6. McKenzie. The Water-works of Southington, Conn. Trans. Am. Soc. 

C. E., 1886, xv. p. 885. 


* Portland cement. 












388 MASONR Y DAMS. 

7. The New Water-works at Bridgeport, Conn. Eng. News, 1887, xvn. 

p. 230. 

8. Fteley. High Masonry Dams. Eng. News, 1888, xix. pp. 74, 92. 

9. Rock-fill Reservoir Dams. Eng. News, 1888, xx. p. 69. 

10. Strains in Curved Dams. Eng. News, 1888, xx. pp. 429, 513. 

11. Schuyler. The Construction of the Sweetwater Dam. Trans. Am. Soc. 

C. E., 1888, xix. p. 201. 

12. Francis. High Walls or Dams to Resist the Pressure of Water. Trans. 

A. Soc. C. E., 1888, xix. p. 147. 

13. Report of the Board of Experts on the Quaker Bridge Dam. Eng . 

News , 1888, xx. p. 344. 

14. The New Bear Valley Dam. Eng. News, 1889, xxn. p. 484. 

15. Strains in Curved Dams. Eng. News, 1890, xxiv. p. 148. 

16. The Greenville, S. C., Water-works. Eng. Record, 1892, xxvi. p. 186. 

17. Jobson. Beetaloo Water-works, South Australia. Proc. Inst. C. E., 

1892- 93, cxin. p. 151. 

18. The New Concrete Masonry Dam of the Butte City Water Company. 

Eng. News, 1892, xxvm. pp. 554, 584. 

19. The Tansa Dam, Bombay Water-works. Engineering, 1892, liii. 

p. 518. 

20. Clerke. The Tansa Works for the Water-supply of Bombay. Proc. 

Inst. C. E., cxv. p. 12. 

21. The New Water-power and Water-supply at Austin, Tex. Eng. News, 

1892, xxvm. p. 152. 

22. Groves. The Austin Dam. Eng. News, 1893, xxix. p. 86. 

23. The Austin Dam Controversy. Eng. Record, 1893, xxvn. p. 155. Also 

various articles in Eng. News, 1892, xxvm. The discussion is 
largely on the question of the flow of water over wide-topped weirs. 

24. Coventry. Note on the Stresses in Masonry Dams. Proc. Inst. C. E., 

1893- 94, cxvi. p. 334. 

25. McCulloh. The Construction of a Water-tight Masonry Dam. Trans. 

Am. Soc. C. E., 1893, xxvm. p. 185. 

26. Kreuter. On the Design of Masonry Dams. Proc. Inst. C. E., 1893-94* 

cxv. p. 63. 

27. The Bhatgur Dam, India. Eng. News, 1893, xxix. p. 391. 

28. Carroll. The Basin Creek Dam for the Water-works of Butte, Mont. 

Eng. News, 1893, xxx. p. 139. 

29. The Beetaloo Concrete Dam. Eng. Record, 1893, xxvm. p. 263. 

30. Pelletreau. Profile sans Extensions des Grands Barrages en Maqonnerie. 

Annales des Ponts et Chaussees, 1894, 1. p. 619. 

31. La Grange Dam for Turlock-Modesto Irrigation Districts, Cal. Eng. 

News, 1894, xxxi. p. 266; Eng. Record, 1894, xxix. p. 216. 

32. Ulrich. Sewall Falls Dam across the Merrimack River, near Concord* 

N. H. Rug. News, 1894, xxxi. p. 326. 

33. Van Buren. Notes on High Masonry Dams. Trans. Am. Soc. C. E., 

1895, xxxiv. p. 493. 

34. The Titicus Dam. Eng. Record, 1895, xxxn. p. 68. 

35. Deacon. The Vyrnwy Works for the Water-supply of Liverpool. Proc. 

Inst. C. E., 1895-96, cxxvi. p. 24. 

36. Intze. Die Erweiterung des Wasserwerkes der Stadt Remscheid. Zeitschr. 

d. Ver. deuisch. Ing. 1895, xxxix. p. 639. Describes a large curved 
dam. Abstract, Eng. News, 1896, xxxv. p. 76. 


LIT ERA TURK. 


389 


37. Schuyler. Water-storage and Construction of Dams. U. S. Geolog. 

Survey, 1896-97, Part IV. p. 617. Describes and illustrates numer¬ 
ous dams. 

38. The Cold Spring, N. Y., Concrete Dam. Eng. Record, 1896, xxxiv. 

p. 105. 

39. Hardesty. The Water-supply System of Salt Lake City, Utah. Eng. 

News , 1896, xxxvi. p. 258. Describes a large concrete dam, 

40. Thompson. The New Holyoke Water-power Dam. Eng. News, 1897, 

xxxvii. p. 292. 

41. Schuyler. The Construction of the Hemet Dam. Jour. Assoc. Eng. 

Soc., 1897, xix. p. 81. 

42. Righter. An Unusual Small Masonry Dam. Eng. Record, 1898, xxxvm. 

P- 559 - 

43. The Power Plant of the Hudson River Power Company, at Mechanicsville, 

N. Y. Eng. News, 1898, xl. p. 130. 

44. The New Croton Dam. Eng. Record, 1898, xxxvm. p. 27. 

45. Rafter, Greenalch, and Horton. The Indian River Dam. Eng. News, 

1899, xli. p. 310. 

46. Concrete Dam for the Vierfontein Water Syndicate, S. Africa. Eng. 

Record, 1899, xxxix. p. 112. 

47. The New Masonry Dam at Holyoke, Mass. Eng. Record, 1899, xl. 

p. 166. 

48. Cone Reservoir Outlet-valves, Plymouth, Eng. Eng. News, 1899, xlii. 

p. 185. 

49. Recent Reservoir Construction, Worcester, Mass. Illustrates small weir. 

Eng. Record, 1900, xli. p. 589. 

50. Gowan. The Foundations of the New Croton Dam. Trans. Am. Soc. 

C. E., 1900, xliii, p. 469. 

51. Lippincott. Exploration for Bed-rock at Gila River Dam-sites with 

Diamond Drills. Eng. News, 1900, xliii. p. 34. 

52. The Wachusett Dam. Eng. Record, 1900, xlii. p. 218. Illustrated 

description of dam and details of gate-chamber. 

FAILURES OF MASONRY DAMS. 

1. Pickey. Failure of Dam at Minneapolis, Minn., Due to Previous 

Weakening through Ice-pressure. Eng. News, 1899, xli. p. 307. 

2. Schuyler. The Failure of the Lynx Creek Masonry Dam, near Prescott, 

Ariz. Eng. News, 1898, xxxix. p. 362. 

3. Failure of the Angels Masonry Dam, Calaveras County, Cal. Eng. 

News, 1895, xxxm. p. 307. 

4. Rider. Defective Dam Construction. Eng. News, 1885, xm. p. 363. 

5. Failure of the Bouzey Dam. Proc. Inst. C. E., 1896, cxxv. p. 461. 

6 . The Failure of the Austin Dam. Full account, including many special 

reports in several of the numbers of ding. Record and Eng. News 
subsequent to the failure, April 7, 1900. 


I 



CHAPTER XVIII. 

TIMBER DAMS; STEEL DAMS; LOOSE-ROCK DAMS. 

TIMBER DAMS. 

450. Use of Timber Dams,—Where a weir is constantly submerged, 
a timber structure is of a permanent nature, and will need repairs only 
on account of the wear of the apron. A timber dam may also be 
advisable in certain circumstances even when its life will be short, as, 
for example, where a temporary supply may be furnished pending the 
construction of more permanent works, or where the expense of 
permanent and costly structures is for the present prohibitory. Such 
dams are, however, used mostly for diversion purposes or for water¬ 
power, and seldom for the storage of large volumes of water. 

Timber dams may be constructed on any kind of a foundation, but 
are usually built on rock or on a gravelly bed. They consist of cribs 
or frames built of logs or squared timber, filled with stone and clay, 
and planked over to rendpr them water-tight. They may be built as 
separate cribs in sections, each section consisting of perhaps 3 to 4 
cribs, or as one continuous framework. The former method is 
especially useful in dealing with large flows and irregular foundations, 
the stream being gradually closed as the sections are constructed. 
The cribs may also be filled and sunk separately so as to form piers on 
which a continuous structure may be built. 

The foundation of a crib dam, if soft, is prepared by dumping stone 
over the area to be built upon. In the framed dam the foundation 
must be more carefully prepared. Where it is soft the dam is supported 
on piling, and sheet-piling is used to prevent underflow. If the dam 
is built on a rock bottom, it must be bolted thereto. The framework is 
usually built with a sloping upper face and a series of stepped aprons 
below, or a single free wall to a water-cushion. Rock and gravel, or 
puddle, is used for filling. 


390 



TIMBER BAMS. 


39 r 


451. Examples of Timber Dams.— Sewall Falls Dam (Fig. 109).—This 
dam across the Merrimack is a crib dam 497 feet long, constructed on a hard- 



Fig. 109.—Sewall Falls Dam. 

(From Engineering News, vol. xxxi.) 

pan foundation. It was built in sections by means of coffer-dams, sluiceways 
being left in the completed portion to carry the water during the construc¬ 
tion of the last sections. The longitudinal pieces are 12 X 12-inch hemlock 
and Southern pine, and the ties 10 X 10-inch hemlock, all fastened together 
by drift-bolts. The spaces were hand-packed with stone. The aprons are 
made of steel on account of heavy ice. The figure shows the construction 
clearly. The life of the structure is estimated by the engineers at fifty to 
sixty years. The cost was about 60 per cent that of a stone dam, the contract 
price being $120,000.* 

452. Bear River Weir. —Fig. no is a section of a timber weir across the 
Bear River, Utah, built to divert water for irrigating purposes. The founda¬ 
tion is solid rock into which the timbers are bolted. All timbers are 10 X 12 



Fig. iio.—Bear River Dam. 

(From Engineering News, vol. xxxv.) 

inch. The interior is filled with stone, and a heavy layer of earth is placed at 
the back to prevent percolation. In the middle of the stream the apron con¬ 
sists of 10 x 12-inch timbers, instead of the second layer of 3-inch plank as 
shown. A portion of the dam founded on gravel and boulders was badly 
underscoured in 1891. This part was afterwards protected by two rows of 
sheet-piling 4 feet apart, driven at the back side, the space between being 


* Eng. News, 1894. xxxi. p. 326. 















































































































































39 2 TIMBER DAMS; STEEL DAMS; LOOSE-ROCK DAMS. 

filled with concrete. The whole was then covered with earth and boulders.* 
453. Buite , Mont ., Crib Dam .— In Fig. 111 is illustrated a crib built at 
Butte, Mont., and notable for its great height. The dotted portion shows the 



Fig. hi.—Timber Dam at Butte, Mont. 

(From Engineering Record , vol. xxxvti.) 

section of the spillway. The height from low water to crest is 56 feet. It is 
founded on a bed of stiff clay and boulders 12 to 35 feet below the surface. 
A concrete wall 4 feet thick extends from the foundation to a point about 
6 feet above the original surface, as shown in the figure. The remainder of 
the excavation is filled with clay puddle, well rammed. The dam is made of 
10 x 12-inch pine timbers and filled with granite packed in layers in the crib- 
work. Soon after completion this structure partially failed under a heavy 
flood. The pressure of the water caused the highest portion to settle or cant 
over (the top moving some 7 or 8 feet down-stream), and the entire structure 
to settle vertically. At one place twenty-seven 12-inch timbers were com¬ 
pressed to a thickness of 24 feet 10 inches. The failure was due to lack of 
resistance to shearing forces, and to the compression of the timbers at the 
joints. The filling was not sufficiently compact to render the structure rigid, 
and no diagonal bracing was used.f 

STEEL DAMS. 

454. Combined Concrete and Steel Dams.— Looking again at the two 
portions of a dam, the impervious part and the supporting part, the 
question arises if a portion of the material of a masonry dam, which 
serves merely as supporting material, might not be omitted, especially 
in the upper parts where the pressures are not great. Such has actually 
been done in at least two cases. The upper face of the dam is made 
in the form of masonry arches, and these are then supported by 
masonry piers. This form of dam is especially useful with difficult 
foundations, as the piers can be separately constructed. 

Fig 112 illustrates the concrete dam at Ogden, Utah, built for the Pioneer 
Power Plant. The piers are concrete walls 16 feet thick with 22 feet in the 
clear, and the concrete arches vary from 6 to 8 feet in thickness The arches 


* Eng. News , 1896, XXXV. p. 84. f Eng. Record , 1898, XXXVII. 


p. 301, xxxviii. p. 203. 



































STEEL DAMS. 


393 


are protected and rendered more impervious by a covering of steel plates, 
although this covering is not essential. In this dam, ioo feet high and 400 



Jy Plan 

Fig. 112.—Concrete Dam, Ogden, Utah. 
ieet long, the quantity of masonry is given as 26,000 cubic yards, as compared 
to 37,200 cubic yards estimated for a dam of ordinary section. The actual 
cost, including steel covering, was 12 to 15 per cent less than that of an 
ordinary dam. The maximum pressure is 10.7 tons. Instead of concrete 
arches, a steel face formed of steel plates was also considered, but was found 
to be more expensive than the adopted design.* 

The other dam of this sort is on the Belubula River, New South Wales. 
It was there adopted on account of the ridgy nature of the bottom. The 
height is 60 feet, length 431 feet, with six buttresses 28 feet apart centre to 
centre, 40 feet long and 5 to 12 feet thick. Brick arches were used, 4 feet 
thick at bottom and 1 foot 7 inches at top, built at an angle of 60 degrees 
with the horizontal.f 


455. Dams Built wholly of Steel. —A dam entirely of steel has been 
built in Arizona, at Ash Fork. The face consists of curved plates -§ 
inch thick imbedded at the bottom in 
concrete. The greatest height is 46 feet. 

The plates are riveted to a system of in¬ 
clined struts resting on a rock founda¬ 
tion. Expansion is taken up by a slight 
bending in the curved plates. Such a 
form as this possesses a great advantage 
in the definiteness with which the stresses 
can be calculated and provided for, and 
the fact that the stability of the struc¬ 
ture is independent of the impervious¬ 
ness of the face. Its chief disadvantages* Fig. 113.—Steel Dam, Ash Fork, 

. . , f . . . 1 Arizona. 

lie in the cost for maintenance ana, prob- 



* Trans. Am. Soc. C E.. 1S07. xxxvm. p. 291. 


f Eng. News , 1898, XL. p. 148. 





























































394 


TIMBER DAMS; STEEL DAMS; LOOSE-ROCK DAMS. 


ably, in its lack of durability, a point not yet well determined. Fig. 
113 shows the form of bracing at the highest portion.* 

A comparative estimate for a 60-foot dam, made in connection with 
the Ogden Dam described above, gave for a steel dam of the form 
shown in Fig. 113 a weight of 7000 pounds per lineal foot; for a 
cantilever design for a steel dam 8050 pounds per lineal foot; and for 
an ordinary masonry dam 48 cubic yards per lineal foot.t 

LOOSE-ROCK DAMS. 

456. Loose-rock Dams.— Dams composed largely of loose rock have 
been used to a considerable extent in the West, and in some respects 
present considerable advantages as to stability. Another advantage is 
that they can be constructed in running water, but the finished dam is 
not suited to act as a waste-weir. 

The body of the dam is made of loose rock placed with more or 
less care, and rendered comparatively impervious by a sheathing of 
plank, or by a facing of earth or fine material on the upper face, or, as 
in one case, by a core of steel. As regards stability the principle of 
construction is of the best. Since considerable percolation is likely to 
take place, such a dam cannot be founded on a material liable to scour; 
and if the dam is high, the foundation should be solid rock. The lower 
slope is usually 1 to 1, while the upper slope may be made J or ^ to 1 ; 
but to secure these steep slopes it is necessary to lay the stone for a 
considerable thickness as a dry wall. Above this wall the facing of 
timber or earth is placed. The former material is objectionable on 
account of its perishable nature. 

Rock-fill dams have been constructed where a stratum of loose 
material of considerable thickness has overlaid the solid rock. In such 
a case, as the dam is built up the loose material gradually scours out 
and the loose rock settles into place. On such a foundation both 
slopes must be made quite flat and no reliance can be placed on re¬ 
taining-walls of any sort. 

A disadvantage of rock-fill dams is in the relatively large loss of 
water which occurs, an important consideration in the case of storage- 
reservoirs. The cost of such dams has in some cases been very low, 
in one instance as low as 45 cents per cubic yard. 

457. Examples. —Fig. 114 shows the section of the dam at Pecos, N. Hex. 
The facing here is of earth. 

A rock-fill dam with timber facing is shown in Fig. 115, the Escondido 
Dam in California. The upper portion of the dam is laid as a dry wall with 

* Eng. News . 1S9S, xxxix. p. 299. 
f Trans. Am. Soc. C. E , 1897. xxxvui. p. 30s, 




LOOSE-ROCK DAMS , 


395 




K - 20 "A 


Fig. 114.—Pecos Dam. 

(From Engineering News, vol. xxxvi.) 



Fig. 115.—Escondido Dam. 


El 130.0 > 16 '* 




Fig. 116. — Lower Otay Dam. 

(From Engineering News, vol xxxix.) 

















































39 6 TIMBER DAMS; STEEL DAMS; LOOSE-ROCK DAMS. 

a thickness of from 5 to 15 feet. The height is 76 feet. The outlet is a 
24-inch cast-iron pipe laid in concrete and having a valve at the upper end.* 
An interesting example of a rock-fill dam is illustrated in Fig. 116, which 
represents the lower Otay Dam in southern California, already referred to on 
page 333 as having a steel core. A masonry dam had been considered for 
this place, but owing to the great depth to bed-rock the plans were changed. 
The construction is clearly shown in the figures. The lower figure shows to an 
enlarged scale the method of joining the steel and masonry core to the founda¬ 
tion at the ends of the dam. The rock forming the dam was placed by 
dumping from a cableway. The leakage is very slight. Other dams of this 
kind have since been constructed. 

LITERATURE. 

TIMBER DAMS. 

1. Parker. Black Eagle Falls Dam, Great Falls, Mont. Trans. Am. Soc. 

C. E., 1892, xxvii. p. 56. 

2. Clarke. Crib Dam. Trans. Am. Soc. C. E., 1895, xxxiv. p. 507. 

3. Hardesty. The Bear River Irrigation System, Utah. Eng. Aews, 1896, 

xxxv. p. 83. 

4. Woermann. A Low Crib Dam across Rock River. Jour. Assoc. Eng. 

Soc., 1896, xvii. p. 54. 

5. Bishop. The Lachine Rapids Power Plant, Montreal, P. Q. Eng. A ews, 

1897, xxxvii. p. 98. 

6. The Butte, Montana, Power Plant. Eng. Record, 1898, xxxvii. p. 301. 

7. Parker. Partial Failure of Timber Dam near Butte, Mont. Eng. Record, 

1898, xxxviii. p. 203. 

8. The Reconstructed Canyon Ferry Dam, near Helena, Mont. Eng. News , 

1900, xliii. p. 266. 

STEEL DAMS. 

1. Thompson. Reservoir Dams, with Iron Sheeting. The Engineer , 1896, 

LXXXI. p. 459. 

2. Steel Weir, Ash Fork, Ariz. Eng. Record, 1898, xxxvii. p. 404; Eng. 

News, 1898, xxxix. p. 299. 

LOOSE-ROCK DAMS. 

1. Wells. The Castlewood Dam. Eng. Record, 1898, xxxix. p. 69. 

2. Parker. East Canyon Creek Dam, Utah. Rock-fill dam with steel core. 

Eng. Record, 1899, xl. p. 313. 

3. The Goose-neck Canyon Dam, Colo. A rock-fill dam 210 feet high with 

steel facing. Eng. Record, 1900, xli. p. 218. 


* Eng . News , 1898, xxxviii. p. 63. 





B. WORKS FOR THE PURIFICATION OF WATER. 


CHAPTER XIX. 

OBJECTS AND METHODS OF PURIFICATION. 

458. Purification of Water for Manufacturing Purposes. —In the puri¬ 
fication of water-supplies, reference is generally made to the treatment 
of water designed for domestic use, but the subject may also be con¬ 
sidered as applied to water intended for manufacturing purposes. 
Generally speaking, in technical industries and for manufacturing pur¬ 
poses a soft water is desired, also one that is free from organic 
impurities. In such industries as brewing, distilling, and sugar and 
starch manufacturing, the question of germ content is more important,, 
as water containing some kinds of micro-organisms is apt to produce 
abnormal fermentations that injure the product. Iron-containing 
waters are particularly detrimental in the manufacture of paper and 
pulp, also in dye-works. These technical industries, however, de¬ 
mand a special examination in selecting a proper source of water- 
supplies, and generally do not pertain to the ordinary work of a water¬ 
works engineer. 

For general manufacturing purposes it is desired that a water should 
not readily form boiler-scale. The precipitation of certain inorganic 
salts, particularly those of calcium and magnesium, interferes much with 
the economic action of boilers as steam-generators. The accumulation 
of this incrustation to a thickness of one-sixteenth inch involves a loss 
variously stated at from 12 to 20 per cent of the energy of the coal 
used. The methods of purifying water so as to remove the mineral 
ingredients capable of forming boiler-scale deserve, therefore, careful 
consideration. 

459. Purification of Water for Domestic Purposes. — In ordinary 
household use the quality of water is of considerable import. Not only 
is a water that is rich in alkaline earths not well adapted for cooking 
and similar purposes, but on account of its action upon soap it is very 

397 


398 


OBJECTS AND METHODS OF PURIFICATION. 


undesirable for general household use. In a hard water, soap is 
decomposed and the fatty acids unite with calcium and magnesium 
salts, forming insoluble compounds under such circumstances. To 
secure the cleansing action, it becomes necessary to use a much larger 
amount of soap. The removal of the hardening impurities of a water 
constitutes, therefore, an important feature of water purification. Its 
economic value is well illustrated by the case of Glasgow already 
mentioned on page 143. 

In purifying a drinking-water there may be two objects in view. 
That which is the most important is the treatment of the water in a 
way so as to remove any danger from pathogenic organisms; in addi¬ 
tion, however, waters may be purified so as to improve their physical 
appearance. This latter object, while it ought to be subordinated to 
the former, often is not, and in the eyes of the consumer an unsavory 
water will often cause more complaint than a pure sparkling water that 
may be polluted with disease organisms. Not all waters destined to 
be used as drinking-water supplies need artificial purification. Ground- 
or spring-waters rarely need to be artificially treated, as they have 
already been purified by the operation of natural forces (Chapter IX). 
They sometimes need treatment for the removal of iron, but generally 
speaking, so far as deleterious bacteria are concerned, they are com¬ 
paratively safe if they are normal ground-waters. 

The waters that need artificial purification most are those that 
remain in contact with the surface of the soil. Not infrequently it is 
possible to secure a surface supply that is perfectly wholesome, but the 
opportunity for pollution is too often present, and the only regions in 
which unpolluted waters are likely to be found are those that are 
sparsely settled. With the increasing density of population, surface 
waters are in general becoming more and more dangerous, until in 
many sections it has become impossible to furnish a supply that is safe 
without the use of some method of artificial purification. This condi¬ 
tion is seen in the steady increase of the typhoid death-rates in many 
of the cities that are supplied with waters from surface sources. 

460. Outline of Methods of Purification Employed. —Numerous pro¬ 
cesses of purification have been devised and tested experimentally to a 
greater or less extent, but in actual practice only a few have been 
found feasible. While many of the methods have been the outgrowth 
of empirical testing, others have been devised as the result of a thorough 
study of the principles that have been found to underlie these processes 
as they occur under natural conditions or where artificially controlled. 

The various processes of purification may be divided into two 


OUTLINE OF METHODS OF PURIFICATION EMPLOYED. 399 

general groups: (i) those for the removal of suspended impurities, and 
\2) those for the removal of dissolved impurities. Of the first class 
there are two general processes, sedimentation and filtration, both of 
which may be called natural processes. By sedimentation, water may 
be more or less freed of its suspended matters, including the bacteria, 
the efficiency of the treatment depending much upon the element of 
time. The process is carried out artificially in large storage-reservoirs 
or in small special settling-basins. It is often aided by the introduction 
T)f some chemical that will produce a precipitate which will readily 
settle and carry down with it the more finely divided matter in suspen¬ 
sion. Variations in the method of operation of settling-basins and in 
the introduction of the chemical give rise to various modifications of the 
general process. 

Filtration is accomplished in different ways. The most common is 
by means of the artificial sand-filter bed, either as contained in masonry 
basins of large size, or confined in small tanks as in the mechanical 
filters. Special forms of filtering media have also been devised, such 
as the Fischer tile filter, also filters made of asbestos, and the various 
forms of small filters for domestic purposes. The chief object is in all 
cases the removal of the suspended matters, and in most public supplies 
particular attention is paid to the removal of bacteria. In many 
instances chemical changes occur in filters, but they are not often of 
any great importance. 

The processes for the removal of dissolved impurities include the 
softening process, in which lime and magnesia are removed by chemical 
precipitation, and the process for the removal of iron in a similar 
manner. Such methods usually involve subsequent sedimentation or 
filtration for the removal of the precipitate. In the iron treatment the 
filtration itself sometimes plays an important part also in the chemical 
changes involved. Aeration consists in bringing air into intimate con¬ 
tact with all parts of the water. This acts both to supply deficient 
oxygen and also to drive out objectionable dissolved gases. It often 
constitutes an important part of other processes. 

Besides the above-mentioned processes there should be mentioned 
the method of purification by distillation, in which practically all 
impurities are removed, and the various methods of sterilization, in 
which the bacteria are simply killed. 

From the preceding statements it will be seen that each problem 
in water purification demands individual treatment ; and that the best 
method to adopt in any case will depend upon the character of the 
water and the use to which it will be put, both of which elements ere 


400 OBJECTS AND METHODS OF PURIFICATION. 

subject to many variations. No one process is universally applicable; 
furthermore, of two processes for removing the same kind ot impurity, 
the most efficient may not in all cases be the best. 1 he highest 
efficiency is not always necessary, and in such cases economy may 
properly be secured by the adoption of a system of less efficiency but 
of lower cost. 


LITERATURE. 

WORKS TREATING OF VARIOUS PURIFICATION PROCESSES. 

1. Delhotel. Traite de PEpuration des Eaux Naturelles et Industrielles.. 

Paris, 1893. 

2. Rideal. Water and its Purification. London, 1897. 

3. Hill. The Purification of Water-supplies. New York, 1898. 

4. Fuller. Water Purification at Louisville. New York, 1898. Report of 

extensive experiments on sedimentation, sand and mechanical filtra¬ 
tion, and the use of coagulants. 

5. Fuller. Report on Water Filtration at Cincinnati. City Doc., 1899. 

Experiments on sedimentation, sand and mechanical filtration, and 
the use of lime as a coagulant with subsequent filtration through 
polarite. 

6. Hazen. Report to the Filtration Commission, Pittsburgh. City Doc., 

1899. Experiments on sand and mechanical filtration and the 
Fischer tile system 

7. Hazen. The Filtration of Public Water-supplies. New York, 1900. 

Treats of filtration, coagulation, and removal of iron. Contains 
bibliography. 

8. Report on Water-purification Experiments at Washington, D. C. Senate 

Doc. No. 259; Fifty-sixth Cong., First Sess. Abstract, Eng. News, 

1900, xliii. p. 315. Sand and mechanical filtration. 


CHAPTER XX. 


SEDIMENTATION. 

461. In the case of many surface supplies the water contains at 
various times large quantities of suspended matter, either with or with¬ 
out more serious polluting substances; and a considerable part of the 
work of purification consists in the removal of this suspended matter so 
as to improve the physical appearance of the water. 

462, The Character of the Suspended Matter. —In streams such as 
would be considered suitable as sources of supply the sediment is prin¬ 
cipally of an inorganic nature, consisting of particles of sand and clay 
of various sizes. There is also usually a small amount of organic 
matter, and, in addition, varying numbers of bacteria, which, although 
too minute to render the water turbid, yet are of the greatest impor¬ 
tance on account of their possible relation to disease. During seasons 
of high turbidity, the bacterial content is usually very high owing to 
the large numbers derived from the surface drainage of the soil. 
Varying numbers may also be derived from sewage pollution, but the 
bacteria from this source are relatively more numerous during the 
seasons of low water when the turbidity is at a minimum. The amount 
and character of the sediment varies greatly from time to time, as 
pointed out in Chapter IX; it depends largely upon the stage of water 
in the different tributaries, and upon the geological character of the 
various parts of the drainage-area. Thus Fuller found that the amount 
of sediment in the Ohio River water at Louisville varied from 1 to 5000 
parts per million, ranging ordinarily from 100 to 1000; and that the 
bacteria varied from a few hundred per c.c. to as high as 50,000.* 
The size of the suspended particles also varies greatly. In some 
waters the finer particles of clay are less than 0.00001 inch in diameter, 
which is smaller even than bacteria. This great variation in amount 
and kind of sediment constitutes one of the most troublesome factors 
in connection with purification works for river supplies. 

* Water Purification at Louisville, 1898, p. 15. 

401 






4 02 


SEDIMENTA 7 'ION. 


463. Limitations of Artificial Sedimentation. —In Chapter IX the 
marked effect of natural sedimentation upon the character of water in 
rivers and lakes was pointed out,—such effect, for example, as may be 
observed in any natural lake or pond fed by sediment-carrying streams. 
Where the body of quiescent water is sufficiently large, and the period 
of repose sufficiently long, this action of sedimentation becomes practi¬ 
cally perfect, and a clear and greatly improved water is the result. 
Artificially, such high efficiency is often obtained where the water is 
collected in large impounding-reservoirs holding several months’ sup¬ 
ply. Where, however, the supply is taken directly from a large 
sediment-bearing stream, very large reservoirs are usually impracti¬ 
cable on account of the great cost; and the period of time during which 
sedimentation can be operative must therefore be limited to a few days 
or even to a few hours. Such a limited amount of sedimentation is, 
however, of much value. 

In general the longer the time of storage within practicable limits 
the better the result; but the value of large reservoirs lies not only in 
the length of time allowed for settlement, but also in the opportunity 
thus afforded for shutting off the river supply at times of great turbidity. 
This is an especially valuable feature in the case of streams of moderate 
size where the high-water stage lasts but a few days. Its value in 
water purification has been long recognized in England. In cities 
where an elevated location can be found for a storage-reservoir so that 
it may also act as a distributing-reservoir, the advantages above noted, 
together with those pertaining to the matter of distribution, would 
properly lead to the adoption of relatively large sizes. (See Chapter 
XXVII for further discussion of distributing-reservoirs.) 

Where a water contains little that is objectionable besides the 
inorganic sediment, a degree of purification can often be obtained by 
mere sedimentation which will render the water fairly acceptable. In 
many instances, however, a satisfactory water cannot be obtained with¬ 
out subsequent filtration; but in this ^ase the process of sedimentation 
constitutes a very valuable and almost indispensable prerequisite to the 
final treatment. For a sewage-polluted water, sedimentation alone is 
an inadequate treatment, as the bacteria are not eliminated in sufficient 
numbers to insure safety. 

464, Methods of Sedimentation. —There are two methods to be con¬ 
sidered: (1) Plain sedimentation; (2) Sedimentation with the addition 
of a coagulant. 


PLAIN SEDIMENTATION. 


403 


PLAIN SEDIMENTATION. 

465. Action of Subsidence. —The particles of sand and clay have a 
specific gravity of about 2.6; they are therefore held in suspension only 
by virtue of the currents maintained in the water. When these 
currents become retarded the suspended matter is gradually deposited, 
the rate of settling varying with the size and form of the particles. 
The weights of similar particles are proportional to the cubes of their 
diameters, while the surface areas are proportional to their squares; 
consequently the relative resistance to sedimentation is much greater 
with fine particles than with coarse. Very weak currents maybe suffi¬ 
cient to hold fine particles in suspension, while the coarser material 
readily settles. To cause the deposition of the finer sediment it is 
therefore necessary for the water to be brought as nearly as possible 
to a state of rest. Indeed the extremely small clay particles and the 
bacteria are probably carried down not so much by their own weight 
as by their becoming entangled with the larger masses. In the case 
of the Mississippi at St. Louis, it is practically impossible to clarify the 
water in the spring by simple sedimentation, owing to the attenuated 
and colloidal condition of the clay particles. 

466. Time Required for Subsidence. —The time required for complete 
sedimentation is very different for different waters, and to determine this 
period recourse must be had to actual experiments. For some waters 
it requires weeks and even months to remove all the turbidity, while 
for others a settlement of a day or two accomplishes fairly good results. 
If the amount of suspended matter is measured by weight, a large pro¬ 
portion will settle in one or two days; but the reduction in turbidity is 
not correspondingly great, as it is the finer portions which exert the 
greatest influence upon the appearance of a water. 

For plain sedimentation a period of 24 hours’ subsidence is about 
the minimum limit adopted, but this will seldom give a clear water. 
A considerably longer time is often necessary to give acceptable 
results. At St. Louis, 24 hours is the standard, but often the results 
are not good. At Cincinnati it is planned to allow at least three days, 
but here the treatment is intended as a preparation for filtration. The 
rate of improvement at Cincinnati is indicated by the results of some 
experiments on small settling-tanks. The average removal of sus¬ 
pended matter was as follows:* 


* Report on Water Purification at Cincinnati, p. 126. 




404 


SEDIMENTA T 10 N. 


Time of Subsidence. 

24 hours.. . . 

48 “ 

72 “ ... 

96 “ ... 

The percentage of removal was greatest when the amount of suspended 
matter was greatest. 

Water from the Covington, Ky., reservoir which had settled about 
30 days was found by Fuller to contain at one time as high as 50 parts 
per million of clay. At Louisville, Fuller concludes that the economi¬ 
cal limit of plain subsidence is about 24 hours, during which time 75 
per cent of the suspended matter is removed. Further preparation is. 
there deemed necessary even for filtration. Where the water is to be 
filtered after sedimentation, the time of subsidence and the efficiency 
desirable become largely matters of economy with respect to the opera¬ 
tion of the entire purification plant. 

467. Bacterial Efficiency of Sedimentation. —In discussing the bac¬ 
terial efficiency of plain sedimentation, it must be remembered that any 
data gathered under ordinary conditions may possibly be misleading, 
as in the case of natural sedimentation in lakes, because of the opera¬ 
tion of other factors, such as light, etc., that may also act as more or 
less effective agents in purification. The effect of sedimentation alone 
can be most accurately determined by considering the phenomenon as 
occurring in covered reservoirs where the direct disinfecting action of 
light and its indirect effect as modifying the development of algae might 
be excluded. This condition precludes the study of the question on a 
large scale, as it is impracticable to cover reservoirs that are large 
enough to permit of storage for a considerable period of time. In lieu 
of any data under these conditions reference must needs be made to' 
studies on sedimentation in open reservoirs. The conclusions drawn 
from such studies are strictly applicable only to reservoirs under like 
conditions. 

The monthly results obtained by the Chelsea Water Company of 
London in 1896 are given in Table No. 61.* (Time of storage 
twelve days.) 

The effect of the time factor in sedimentation is more clearly seen 
by reference to the data given in Table No. 62 relating to experiments 
made at the St. Louis settling-basins. + 


Amount of Suspended 
Matter Removed. 

. . 62 per cent. 

. . 68 
. . 72 “ 

. . 76 


* Hill. Public Water-supplies, 1898, p. 144. 
f New York State Board of Health, Report 1893, p. 711. 








PLAIN SEDIMENTATION. 


405 


TABLE NO. 61. 

BACTERIAL EFFICIENCY OF STORAGE AND FILTRATION, CHELSEA WATER CO., LONDON 


Month. 

Bacteria per Cubic Centimeter. 

River Thames. 

After 12 Days’ 
Storage. 

After 

Filtration. 

Januarv. 

11,560 

1360 

20 

February. 

26,800 

460 

44 

March. 

18,000 

240 

28 

April. 

7,520 


A 




May. 

2,060 

140 

24 

Tune. 

6,760 

1150 

178 

July. 

2,220 

420 

20 

August.. 

1,740 

200 

18 

September. 

4,300 

140 

2 

October. 

39,760 

340 

8 

November. 

8,560 

280 

12 

December. 

160,000 

354 

55 

Average. 

24,107 

508 

34 


Average percentage reduction by subsidence, 97.85. 

Average percentage reduction by subsidence and filtration, 99.86. 

Results obtained by other London works ranged from 49 to 85 per cent average 
reduction for periods of subsidence varying from 3.3 to 15 days. 

TABLE NO. 62. 

BACTERIAL RESULTS OF STORAGE AT ST. LOUIS. 


Time of Standing. 

No. of Bacteria per c.c. at Different Depths. 

2.5 Feet. 

5 Feet. 

7.5 Feet. 


6510 

1970 

2960 

I day... 

6290 

2990 

880 

2 days. 

230 

320 

200 

3 days. 

200 

200 

200 


The effect of long subsidence is shown by the following typical 
figures relating to the number of bacteria in the Ohio River water as 
supplied to Cincinnati, Ohio, and to Covington, Kentucky. In Cin¬ 
cinnati the water had little or no sedimentation, while at Covington the 
large reservoir furnished about 30 days’ subsidence.* 

At Cincinnati Fuller found in his experiments that about 75 per 
cent of the bacteria were removed by three days’ subsidence.t 


* Report of Engineer Commission of Cincinnati Water-works, 1896, p. 15. 
f Fuller. Cincinnati Report, p. 128. 




















































406 


SEDIMENTA TION. 


TABLE NO. 63 . 

BACTERIAL RESULTS OF STORAGE AT CINCINNATI AND COVINGTON. 


Date. 

Bacteria per Cubic Centimeter. 

Cincinnati. 

Covington. 

Reduction by 
Sedimentation, 
Per cent. 

January 23, 1896. 

1599 

194 

87.87 

February 4, 1897. 

1656 

53 

96.80 

“ 17. 1897. 

684 

20 

97.08 

“ 26, 1897. 

1436 

102 

92.90 


Notwithstanding there is a marked degree of purification where 
rehance is placed merely on subsidence, yet it should be kept in mind 
that such a method is extremely hazardous, especially where the water- 
supply is subject to any sewage-pollution. This is strikingly shown in 
the case of the Lawrence reservoirs that used to hold from io to 14 
days’ supply and in which there was a reduction of about 90 per cent 
of the bacteria present in the river-water; still such purification was 
insufficient to protect the supply, as is evidenced by the fact that the 
typhoid death-rates of this town were exceptionally high for many 
years. 

468, Bacterial Content of Reservoir Sediment. —It must be remem¬ 
bered that while subsidence removes bacteria from the water, it is only 
to accumulate them in relatively larger quantities in the mud and ooze 
at the bottom of the reservoir (Art. 180). Not only do they accumu¬ 
late here from deposition from superincumbent waters, but actual growth 
occurs in abundance in the rich organic matter of lake bottoms. 
Russell * found the germ content in the water and mud of the bay of 
Naples to be as given in Table No. 64: 

About one-half of the species present in the mud were indigenous 
to this habitat, while the remainder were common to both water and 
mud. He finds that the same principle also obtains in waters of fresh¬ 
water lakes. In the layer of ooze taken from the reservoirs of the 
Altona Water-works,t which is supplied with Elbe River water, there 
were found 17,000,000 bacteria per c.c., while the water just over this 
slime had upwards of 1,000,000 for same volume.^ 


* Zeit. f. Hyg., 1891, xi. p. 177. 
f Cent. f. Bakt., 1S98, XVI. p. 881. 

% See also Lortet, Pathogenic Bacteria in Mud of Geneva Lake. Cent. /. Bakt. y 
1891, ix. p. 7og 0 



















PLAIN SEDIMENTATION. 


40 7 


TABLE NO. 64 . 

BACTERIA IN WATER AND MUD OF BAY OF NAPLES. 


Depth of Water. 
Meters. 

No. of Bacteria per Cubic Centimeter. 

In Water. 

In Mud. 

50 

121 

245,000 

TOO 

IO 

200,000 

200 

59 

70,800 

300 

5 

24,000 

400 

3 ° 

22,000 

500 

22 

12,500 

IIOO 


24,000 


469. Experimental Data on the Action of Finely Divided Matter in 
Water, —Abundant experience has demonstrated the value of copious 
amounts of suspended matter in purifying waters by sedimentation. 
In the light of this fact, the following experiments made by Frankland * 
are of interest in showing the value of different solids in purifying water 
by agitation and subsequent subsidence. These trials were confined 
for the most part to laboratory conditions, but they illustrate the prin¬ 
ciple involved in this type of purification. Water was shaken up for a 
definite length of time with finely divided sterilized material of uniform 
size and then allowed to clarify itself by sedimentation. The clear 
supernatant water was then examined bacteriologically with the results 
given in Table No. 65. 


TABLE NO. 65 . 

PURIFICATION OF WATER BY AGITATION WITH FINELY DIVIDED SOLID MATTER AND 

SUBSEQUENT SUBSIDENCE. 



Spongy 

Iron. 

Chalk. 

Animal 

Charcoal. 

Vegetable 

Charcoal. 

Coke. 

Amt. of suspended matter (by wgt.) 

i : 10 

1 : 50 

I : 50 

W 

u\ 

0 

I : 50 

No. of bacteria per c.c. before treat- 
ment. 

609 

8000 

8000 

3000 

very 

No. of bacteria per c.c. after treat¬ 
ment for 15 minutes. 

63 

270 

60 

120 

large 

0 

Percentage reduction. 

90 

97 

99 

96 

IOO 


* Proc. Roy. Soc., 1885. Proc. Inst. C. E., 1886, lxxxv. p. 197. 



























408 


SEDIMENTA TION. 


SEDIMENTATION WITH COAGULATION. 

470. The Use of Coagulants. —Various chemicals when added to 
water will combine with certain substances ordinarily present, forming 
precipitates which are more or less gelatinous in character. These 
act as coagulants to collect the finely divided suspended matter into 
relatively large masses which are much more readily removed by sedi¬ 
mentation or filtration. Color may also frequently be removed to a 
large extent by this treatment. The use of coagulants in water purifi¬ 
cation is as yet (in 1900) almost entirely confined to their employment 
in connection with mechanical filters (see Chapter XXII), but they 
have been used to good advantage in a few instances with sand filters, 
and quite recently in a few places where sedimentation is the only 
treatment. If a water can be satisfactorily purified the greater part of 
the year by plain sedimentation, the use of a coagulant at other times 
as an aid in the process is well worth consideration. 

471. The Action of Sulfate of Alumina. —Several substances can 
be used as coagulants. That most commonly employed is sulfate of 
alumina. When this substance is introduced into water containing 
carbonates and bicarbonates of lime and magnesia, it is decomposed, 
the sulfuric acid forming sulfates with the lime and magnesia, while the 
carbonic acid is set free, and the alumina unites with water to form a 
bulky gelatinous hydrate which constitutes the coagulating agent. 
According to Fuller, part of this hydrate may be absorbed by the clay 
particles before much coagulating action takes place, the amount 
absorbed depending upon the amount and character of the sediment. 
If more sulfate is used than can combine with the quantity of car- 
bonates present, it will remain dissolved in the water, a result which is 
necessary to avoid on account of the possible injurious effect of the 
alum. When such water is distributed in iron pipes, the acid-reacting 
water is apt to rust the pipes, giving a disagreeable iron taste to the 
water. If the water does not naturally contain a sufficient amount of 
alkalinity to decompose the necessary amount of coagulant, lime should 
be previously added to the water. Theoretically, one grain of sulfate 
will decompose about 8 parts per million of CaCO., or its equivalent, 
but owing to the absorptive action previously mentioned the actual 
reduction of alkalinity is likely to be less. Experiments on the Ohio 
River water at Louisville indicated a reduction of alkalinity of from 65 
to 85 per cent of the theoretical amount when the suspended matter 
amounted to from 1200 to 200 parts per million. It was also shown 


THE USE OF COAGULANTS. 409 

that much more coagulant was required with fine sediment than with 
coarse. 

Accompanying the reduction of the carbonates is an equal increase 
in the sulfates of lime and magnesia. As these compounds form the 
objectionable incrusting constituents or the permanent hardness of a 
water, this change is detrimental. With the ordinary quantities of 
coagulant used, such as 1 to 2 grains per gallon, this increase in hard¬ 
ness would amount to from 9 to 18 parts per million, not relatively a 
very important matter, and probably much overbalanced by the gain 
in clearness of the water. This objectionable increase in the permanent 
hardness may be avoided by the use of sodium carbonate instead of 
lime (Art. 558). 

The amount of carbonic acid set free is equal to 44 per cent of the 
decrease in carbonates. This acid remains absorbed in the water and 
increases its corrosive action on unprotected iron plates, which is, how¬ 
ever, not a serious matter. If the carbonate is all or nearly all reduced, 
there is more danger of solvent action on lead pipes. 

472. The Amount of Chemical Required. —This depends upon the 
amount and character of the sediment, upon the degree of purification 
desired, and upon the time of settlement. It varies in practice from 
about f grain to 3 or 4 grains per gallon. The proper amount can 
only be determined by experiment. Some idea of the amount required 
can be had from the data of Table No. 66, compiled by Hazen. This 
gives the approximate amount of chemical required for the Ohio River 
water at Cincinnati* and the Allegheny River water at Pittsburgt as 
a preparation for filtration. In general the more chemical used the 
greater the effect, and by using a sufficient quantity and allowing 
enough time for sedimentation a clear water can be secured. But the 

O 

question of economy will usually limit the efficiency obtained, and 
where the process is but a preliminary treatment a high degree of 
efficiency is not necessary. 

473. Time of Subsidence. — The rate of sedimentation depends 
greatly upon the amount of coagulant employed. It takes place much 
more quickly than where no coagulant is used, so that a large part of 
the action will occur in a few hours. With a fair amount of coagulant, 
the sediment remaining after 24 hours’ subsidence will settle very 
slowly; and this period may be taken as about the maximum economi¬ 
cal figure. Much less time than this can be used in many cases. The 
question of amount of sediment, of chemical needed, and time of sub- 


* Cincinnati Report, pp. 290, 341. 

f Report of the Pittsburg Filtration Commission, 1899. 




4 io 


SEDIMENTA TION. 


sidence are intimately related, and the best and most economical 
arrangement must be worked out for each case by itself. 

TABLE NO. 66. 

ESTIMATED AVERAGE AMOUNTS OF REQUIRED CHEMICAL FOR DIFFERENT GRADES OF 

WATER (HAZEN). 


Suspended 

Matter. 

Parts 

per Million. 

Chemical Required. 

Grains per Gallon. 

Raw Water for 
Sand Filters. 
Cincinnati. 

Subsided Water 
for Sand 
Filters. 
Cincinnati. 

Subsided Water 
for Mechanical 
Filters. 
Cincinnati. 

Minimum for 
Raw Water for 
Mechanical 
Filters. 
Pittsburg. 

10 

0 

O 

0.75 

O.40 

25 

O 

O 

I.25 

O.50 

50 

O 

O 

1.50 

O.70 

75 

O 

I.30 

1-95 

O.90 

100 

1.50 

I.60 

2.20 

I. OO 

125 

I.60 

I.80 

2-45 

1.15 

150 

1 .70 

2.00 

2.65 

1.30 

175 

1.80 

2 . IO 

2.85 

1.40 

200 

1-95 

2.20 

3.00 

I.60 

300 

2.25 

2-45 

3.80 

2.00 

400 

2.50 

2.75 

4.40 

2.50 

500 

2.80 




600 

3-05 




750 

3-40 




1000 

4.00 




1200 

4-75 





Where the water contains large amounts of sediment, it will often 
be more economical to allow the coarser particles to settle before 
applying the coagulant. This will reduce the cost of chemicals and 
give a more satisfactory result. 

474. Efficiency of Sedimentation with Coagulation. —As previously 
stated, the efficiency is a function of the time, amount of coagulant, and 
character of the sediment. The bacterial efficiency follows in a 
general way the efficiency with respect to the suspended matter. 
Bacterial examinations of water from the settling-tanks connected with 
mechanical filters at Louisville showed a removal in the very short time 
there allowed for sedimentation (less than one hour) of ordinarily from 
40 to 75 per cent of the bacteria. The removal of other suspended 
matter was scarcely more than this. When allowed to stand over¬ 
night, or over Sunday, the removal of both bacteria and suspended 
matter was practically always over 90 per cent. With large amounts 
of coagulant, such as 5 or 6 grains per gallon, very high efficiencies 
may be reached. 













THE USE OF COAGULANTS. 


411 

The removal of color depends much upon the nature of the water. 
Usually from jo to 90 per cent of the color of ordinary peaty water 
may be removed by suitable quantities of chemical, but some waters, 
especially those having a high color, cannot readily be decolorized in 
this way. At Superior, Wis., the use of four grains of sulfate per 
gallon had no appreciable effect on a water having a color of about 2 
on the platinum scale. 

475. Action of Coagulants other than Sulfate of Alumina.—Potash 
alum is sometimes used as a coagulant, but as it costs about the same 
as the sulfate and contains less aluminum, there is nothing to be gained 
by its use. Various compounds of iron have also been used more or 
less for this purpose. In this case it is the ferric hydrate which forms 
the coagulant. This substance can be obtained by adding ferric sulfate 
to the water. It acts very much the same as aluminum sulfate, and 
has practically the same efficiency. Another way of obtaining this 
hydrate is by the use of metallic iron, as in the Anderson process 
described later (Chapter XXIII). In this case the metallic iron forms 
ferrous carbonate with the carbonic acid present, which in turn oxidizes 
to the ferric hydrate from the oxygen dissolved in the water. 

Both the aluminum and the ferric hydrate can be produced electro- 
lytically from the metals. The expense of metallic aluminum as com¬ 
pared to the sulfate precludes the use of that metal, but it is possible 
that in some cases the ferric hydrate might be economically produced 
in this way. (For further discussion see Chapter XXIII.) 

Lime is another substance that may be used as a coagulant. When 
used in the ordinary Clark process for softening water the effect is con¬ 
siderable, but still greater effects can be obtained by using lime in 
moderate excess. Naturally the pulverulent precipitate of lime car¬ 
bonate is generally not nearly as effective as the gelatinous alumina 
precipitate. Experiments involving this process at Cincinnati, Ohio, 
showed the following average results:* 



River Water. 

Effluent. 

Per cent 




Removed. 

Suspended matter (parts per 1,000,000). 

273 

35 

87.2 

Bacteria (per c.c.). 

23,800 

1300 

94-5 


The average period of subsidence was about 14 hours, and the average 
amount of lime used was 4.7 grains per gallon, of which 3.1 grains was 


* Cincinnati Report, p. 483. 















412 


SEDIMENTA TION. 


in excess of the amount required to combine with the bicarbonates. 
This excess of lime involves a further process for its removal, which 
may consist in the addition of carbonic acid. 

In some cases the coagulating agent, if added in large quantities, 
produces not only the mechanical effect of sedimentation due to the 
settling of the precipitate, but the excess of chemical used may act as 
a direct germicide on the bacteria present. Such treatment, however, 
is inapplicable for water-purification, although it is sometimes used in 
the treatment of sewage. 


SETTLING-BASINS. 

476. Settling-basins are constructed in accordance with the same 
general principles as other reservoirs; in fact in many cases distribut¬ 
ing-reservoirs or storage-reservoirs act also as settling-basins. Where, 
however, but a short time is allowed for settling, and reservoirs are 
intended for that special purpose, there are differences in detail which 
should be considered. Settling-basins are usually supplied with water 
by means of low-service pumps, and from the basins the water flows 

v into an equalizing clear-water reservoir, or to a pump-well, or to filters, 
as the case may be. 

477. Methods of Operation.—There are two general methods of 
operating settling-basins: (1) the constant-flow method, and (2) the 
intermittent or fill-and-draw method. In the former the water is 
allowed to flow at a very slow velocity through one or more reservoirs, 
during which time the settling takes place. In the latter, the water is 
let into a basin and allowed to remain quiescent during the period of 
subsidence. It is then drawn off to as low a level as efficient clarifica¬ 
tion has taken place, and the basin refilled. It is probable that certain 
waters can be treated best by one system and others by the other 
system, but this is a matter which can only be determined by experi¬ 
ment. 

The method of fill-and-draw, used at St. Louis, is thought by the 
engineers in charge to be more suitable for conditions at that place. 
Some experiments made to determine this point appear to bear out 
this opinion, but they were hardly extensive enough to be at all con¬ 
clusive. In several plants using Missouri River water the constant-flow 
system is used. At Cincinnati, Ohio, the fill-and-draw method is 
used, but it is stated that this is on account of matters pertaining to the 
form of the basins which are purely local in character. * In the fill-and- 
draw method no settlement of fine particles can commence until the 


SE TTLING-BA SINS. 


413 


operation of filling is completed, which condition materially reduces 
the time of subsidence. On the other hand the water becomes 
more quiet than in the other process, and this operates to its 
advantage. 

Independent of the question of clarification, a disadvantage of the 
intermittent-flow method is in the loss of head occasioned by its use. 
Thus the highest level of the water in the clear-water basin or in the 
filters must be as low as the lowest point at which the water is drawn 
off. This not only increases the expense of pumping, but is an 
arrangement not always easy to make. In the constant-flow system 
practically no head need be lost in the settling-basins. It should be 
noted, however, that basins on the fill-and-draw method can be utilized 
more or less as storage-reservoirs, which cannot be done with the 
others. This gives more elasticity to the system and admits of a freer 
operation of the supply-pumps. 

478. Number and Size of Basins.—If the basins are operated on the 
constant system, a single basin can be made to suffice, an arrangement 
quite suitable for a relatively clear water where sedimentation is a 
secondary matter, or merely a preparation for filtration. If there is 
much sediment, at least two basins are needed, in order that one may 
be cleaned without interrupting the supply. In case a coagulant is 
used after partial sedimentation, two. basins would be necessary and 
three would be desirable. With the fill-and-draw method, the number 
becomes a question of economical construction and operation. The 
basin being filled is not effective, and that being drawn from may be 
counted as one-half effective, so that if q is the capacity of each, A the 
volume of consumption for the selected time of settlement, and n the 
number of basins, then 


n = — + 

that is, the required number is equal to the fixed volume A divided by 
the capacity q, plus ij. The larger the value of q, the lower will be 

the cost of the — basins, but the higher will be the cost of the extra 

<1 

i± basins. The best capacity and number can readily be determined 
by trial estimates. At St. Louis, the best number was found to be 
from 6 to 8. 

479. Form of Basin.—For a single rectangular basin of given area 
the square is the most economical form. For a number of basins the 


4*4 


SEDIMENTA TION. 


best proportions may be determined by trial esti¬ 
mates, but the following analysis will be of some 
assistance in arriving at an approximate solution: 

Let n = number of basins, each of which has a 
width b and length a (Fig. 117). Let c e — cost per 
lineal foot of exterior wall or embankment, and 
c i — cost of interior wall or embankment. Then if C — total cost of 
embankments, we have 



C — (211b —j- 2 ci^c e — J— ('11 % . . . (1) 

A 

Let ab = A, a constant quantity. Then b — —. Substituting this 
value in the above equation, we have 

A 

C — (2 n - 1 - 2 a)c e + (11 — 1 )aci .(2) 

& 


Differentiating with respect to a , equating to zero, etc., we find that 
for a minimum value of C the value of a is 


2 nbc e 

2 c t + (n — 1 y; 


b 2 + ( n ~ 

whence — = - 

a 2 n 




If = c { , 


then 


b n + I • 
____ * • 

a ~~ 2 n ’ 


which gives for n= 2, b =ja; for 


n— 3, b — \a, etc. 

The above results are seen to be independent of the area, and hence 
are true for basins or reservoirs of any size, arranged in the manner 
shown. 

In general, settling-basins are built similar to ordinary reservoirs, 
partly in excavation and partly by embankment, so as to secure the 
greatest economy. Earthen slopes will usually be cheaper than 
masonry walls, but with the fill-and-draw method the former have the 
disadvantage of exposing the mud at each period of emptying. They 
are, however, more often used in spite of this. The depth of basins is 
made about such as to give the most economical construction, very 
shallow basins being avoided. The time of settlement is found not to 
be materially affected by depth. 

480. Arrangement of Pipes, Continuous-flow System. — The object 
to be attained in this system is the distribution of the water on entering 
as evenly as may be across one side or one end so that it shall enter 
with as little disturbance as possible; then to draw it off in a similar 














SETTLING-BA SINS. 


415 


manner from the opposite side, and from the stratum of clearest water. 
As far as possible all parts of the water should remain in the basin 
equal lengths of time, and all strong currents should be avoided. The 
ordinary inlet is usually a single large pipe laid through the embank¬ 
ment, or a single sluice-gate in a gate-chamber built in the walls. A 
better distribution of the water could be obtained by means of several 
inlets, or several branches from a single inlet-pipe. These inlets may 
be separately controlled, or, if economy is necessary, the main inlet- 
pipe may be laid inside the basin along one side or end and be provided 
with several open branches. If the water at the surface of the reser¬ 
voir is warmer than the entering water, as will usually be the case, 
then a more uniform movement will be caused if the water enters near 
the bottom. 

The withdrawal of water in this system should take place from near 
the surface. Broad weirs formed in the wall, or made of iron troughs, 
are frequently used. In cold climates, where this arrangement would 
cause trouble by ice, the weirs may be submerged a short distance in 
cold weather by raising the outlet-level. Instead of weirs, a series of 
vertical pipes open at the upper end may be used, as in the Albany 
settling-basin described on page 418. At Denver the water flows off 
over a very large number of circular weirs fitted to verlical effluent 
pipes. Formerly it was the practice to introduce diaphragms or par¬ 
titions in a settling-reservoir to cause a circulation throughout, but 
this defeats the very end sought to be obtained in the way of quiescent 
water. Uniformity of flow and low velocities are the conditions 
desired, and these can best be secured by numerous or broad inlets 
and outlets. 

481. Arrangement of Pipes, Intermittent System.—In this system, 
since the water may enter rapidly, the inlet is arranged in the simplest 
way, as in an ordinary reservoir. The position of the outlet is of more 
importance. If but a single one is used, it will need to be at the 
lowest point of outflow, and so will not draw from the clearest stratum 
except near the end of the operation. The difference in clearness at 
different depths after 24 hours’ subsidence or more is, however, not very 
great. At St. Louis, observation showed that there was very little 
difference in clearness from top to bottom, and but a single outlet was 
there provided. Experiments at Cincinnati* showed that the upper 
6 inches was considerably clearer than the water lower down, but that 
below this there was little change. The results of the experiments are 
given in Table No. 67. The time of settlement was 72 hours. 


* Report on Purification, p. 121. 




416 


SEDIMENTA TION. 


TABLE NO. 67 . 

EXPERIMENTS ON SEDIMENTATION AT CINCINNATI. 


Depth of Sample. 
Feet. 

Suspended Matter. 
Parts per Million. 

Percentage 

Removal. 

0.25 

137 

78.8 

3-00 

190 

70.3 

8.00 

195 

69-5 

13-00 

197 

69.2 

23.00 

206 

67.8 

28.00 

200 

68.7 

30.00 

215 

66.4 

31.00 

200 

68.7 

32.00 

206 

67.8 

33-75 

64I 

00.0 


Unless the water can be drawn from very near the surface little 
advantage is gained in ordinary shallow basins by constructing an out¬ 
let near the top. With a depth such as at Cincinnati, however, there 
would be some advantage in two outlets instead of one. To enable 
water to be drawn always from near the surface, the adjustable outlet- 
pipe described in Chapter XXVII is used to advantage in many 
reservoirs, and among these the new settling-reservoirs at Cincinnati. 

482. Drain-pipes.—To enable the sediment to be removed, the 
bottom of the basin should be made slightly sloping (1 to 2 per cent 
grade) towards a central drain leading to an outlet-gate or to a 
drain-pipe. The mud is removed by flushing it into the drain by 
means of a hose-stream, supplied from a high-pressure main. The 
cleaning is done at intervals depending entirely upon the local condi¬ 
tions, and may be every month or so, or only at intervals of years. 
The longer the mud is allowed to remain the more compact it becomes 
and the more difficult to remove, but the change in compactness takes 
place quite slowly. 

483. Clear-water Well.—Where the basins are operated on the 
continuous-flow system and the water passes from them directly to the 
pumps, it is necessary to interpolate a small clear-water or pump well 
to avoid the necessity of too frequent adjustment of the rate of supply 
to the basins. It is not necessary that the operation be perfectly 
uniform, for the loss in efficiency due to a more rapid motion through 
the basins part of the time is largely compensated by a reduced rate of 
flow at other times. 

484. Examples of Settling-basins.—The St. Louis settling-basins consti¬ 
tute the largest plant of its kind ever built. The general arrangement of 
intake-pumps, basins, and filling and drawing conduits is shown in Fig. 118. 








SETTLING-BA SINS. 


41 7 


The basins are of 22,000,000 gallons drawing capacity each. They are built 
\\i masonry si e and partition walls, and linings of concrete, on about 18 
inches of puddle. Through the centre runs a ditch having a slope of 1 per 
cent, and leading to a 24-inch drain-pipe at the east end. The floor also 


* 



slopes towards this ditch from both sides. The filling is done through a 
60-inch pipe leading from a filling conduit of masonry. The drawing is done 
at the east end through two sluiceways, 4 by 5 feet in size, which take the 
water from about 5 feet above the bottom. The water passes thence through 
a 60-inch pipe into the main delivery-conduit. 


I 























































SEDIMENTA TJON. 


418 

A recent design for a settling-basin is that for the city of St. Joseph, Mo., 
illustrated in Fig. 119, Mr. Wynkoop Kiersted, Mem. Am. Soc. C. E., 
engineer. The following description is from an article by Mr. Kiersted in 
he Engineering Record , 1889, vol. xl. p. 506. 



Fig. 119. — Settling-basin at St. Joseph, Mo. 

(From Engineering Record , vol. xl.) 

“ The water delivered by the low-service pumps enters the basin No. 1 at 
the points A and B either when all three basins are in operation, or when 
basins 1 and 2 are in operation and No. 3 is empty for cleaning; at point C 
when basins 1 and 3 are in operation, and at D when No. 1 is empty for 
cleaning. The continuous method of sedimentation is recommended; conse¬ 
quently communication between the basins is made by weirs. ” When basin 
No. 2 is being cleaned, water enters basin No. 1 at C and overflows the arch 
at E and thence passes through pipe F into the bottom of No. 3. It is pro¬ 
posed to introduce a coagulant into the water as it passes the weirs, through 
a line of small pipe provided with suitable openings. The bottoms of the 
basins slope in each case towards a central gutter from which the sewer drain¬ 
pipes lead. 

The settling-basin at Albany, N. Y., used in connection with the filter- 
plant, possesses several features worthy of notice. (For illustration see page 
437.) The capacity is 14,600,000 gallons, or about i|- days’ supply. The 
operation is continuous, water being admitted through eleven inlets along one 
side and flowing out through an equal number of overflow-pipes on the oppo¬ 
site side. The inlet-pipes rise 4 feet above the water-line and are perforated, 
this causing aeration of the water as it enters. An overflow is provided 
through a manhole as shown on the plan (Fig. 120). A waste or blow-off 
pipe leads from a sump near the centre, towards which point the bottom 
slopes from all directions. As the Hudson River water is clear during a large 
portion of the year, the basin can be readily thrown out of service for 
cleaning.* 


* For full description see Trans. Am. Soc. C. E., 1900, xliii. p. 256. 


























































LI TER A TURK. 


4*9 

* 


LITERATURE. 

(See also references on page 400.) 

1. Seddon. Clearing Water by Settlement; Observations and Theories. 

Jour. Assn. Eng. Soc., 1889, vm. p. 477. 

2. Delafield. The Vicksburg Settling-basins. Trans. Am. Soc. C. E., 1889, 

xxi. p. 88. 

3. Settling-basins for the Low-service Extension of the St. Louis, Mo., 

Water-works. Eng. News , 1891, xxv. p. 380. 

4. Reduction of Bacteria by Sedimentation at Oberlin, O. Eng. Record, 

1898, xxxvii. p. 557. 

5. Gwinn. The Quincy, Ill., Settling-reservoirs. Eng. Record , 1898, 

xxxviii. p. 8. 

6. Bacteria Reduction by Storage at London. Eng. Record , 1898, xxxviii. 

p. 230. 

7. The New Settling and Aerating Basins, Fort Smith, Ark. Eng. News , 

1898, xl. p. 107. 

8. Kiersted. Sedimentation-basins for Water-works. Eng. Record , 1899, 

xl. p. 506. 

9. Kiersted. Reinforcement of the Walls of the Kansas City Settling-basins 

and the Use of a Coagulant to aid Clarification. Eng. News, 1900, 
XLIII. p. 3. * 

10. Sedimentation Tanks with Numerous Overflow Weirs; Denver Union 

Water Co. Eng. News } 1900, xliv. p. 322. 


CHAPTER XXI. 


SAND FILTRATION. 

485. Historical.—The first filter of which we have any record was 
established by Mr. James Simpson in 1829 for the Chelsea Water 
Company of London. The chief object of this filter was to remove 
turbidity, and in this it was a success. Its value in improving the 
water from a hygienic standpoint was also appreciated, although the 
principles underlying its action were not understood until some years 
later. As a consequence of the good results obtained from this filter, 
the filtration of all river-water supplies of London was made compul¬ 
sory in 1855. Similar filter-plants were also soon established at several 
places on the Continent. a 

When efficient chemical methods of water analysis were devised 
about 1870 and applied to the subject of filtration, it was found that 
but little purification, chemically, was effected by the process. The 
result was disappointing, as the organic matter itself was at that time 
considered to be a chief cause of disease. After the establishment of 
the germ theory of disease and the application of modern bacteriologi¬ 
cal methods to water filtration by Prof. P. F. Frankland in 1885, the 
subject was put upon an entirely new and substantial basis; for it was 
found, fortunately, that the sand filter, although showing imperfect 
results from a chemical standpoint, was an excellent medium for 
removing bacteria. It is thus interesting and valuable to note that this 
process, which was developed empirically, really had a scientific founda¬ 
tion. 

Within the last fifteen or twenty years the use of sand filters has 
become almost universal abroad wherever surface-waters are used. In 
Germany it is made compulsory. Hazen estimates that over 20,000,- 
000 people are now supplied with filtered water. In the United States 
it is only very recently that this subject has received the attention that 
it merits. In view of these facts it is interesting to note that as long 
ago as 1869, Mr. J. P. Kirkwood wrote a most valuable report on 



GENERAL DESCRIPTION OF A SAND FILTER . 42 I 

filtration, describing therein many foreign works and recommending 
the adoption of the system in St. Louis. The report at that time 
received comparatively little notice in this country, but was translated, 
and widely circulated in Germany. The recommendations, however, 
were not adopted, but in 1872 a filter was constructed at Poughkeepsie, 
N. Y., under Mr. Kirkwood’s direction, which is still in operation. A 
similar one was built at Hudson, N. Y., in 1874, but no others until 
very recently. Several plants are now in operation, and in 1899 a 
fifteen-million-gallon plant was completed for Albany, N. Y., the 
largest yet constructed in this country. Similar plants are now (1900) 
under consideration for Pittsburg, Philadelphia, Cincinnati, Superior, 
Wis., and several other places. 

The development of the use of filters in the United States in the 
last decade is shown by the following estimate by Fuller A 


1890. 1900. 

Slow sand filters. 

Total area in use (acres). 1.5 19 

Capacity (million gallons per day). 4 57 

Mechanical filters. 

Total area (square feet).. 12,000 90,000 

Capacity (million gallons per day). 36 270 


486. General Description of a Sand Filter,—In the slow sand filter 
as employed almost universally in Europe the sand-bed is constructed 
in large water-tight reservoirs, either open or covered, each having 
usually an area of from ^ to ij acres. On the bottom of the reservoir 
is first laid a system of drains, then above this are placed successive 
layers of broken stone and gravel of decreasing size, and finally the 
bed of from 2 to 5 feet of sand which forms the true filter. The water 
flows by gravity, or is pumped, upon the filter, passes through the 
underdrains to a collecting-well, and thence to the consumer. Water 
containing much sediment is usually first passed through settling-basins, 
where a large part of the sediment is removed. 

As the water filters through the sand, the friction causes some loss 
of head, which gradually increases as the filter becomes clogged with 
foreign matter. The rate of filtration is, however, maintained nearly 
uniform by suitable regulating devices which vary the head according 
to the resistance. When the working head has reached a certain fixed 
limit of a few feet, the water is shut off, the filter drained, and the sur¬ 
face cleaned by removing a thin layer of clogged sand. The operation 


* Report Am. Pub. Health Assn., for 1900. 






SAND FILTRATION. 


4 22 

is then resumed. Before the thickness of the sand layer becomes too 
greatly reduced, clean sand is added sufficient to restore the filter to 
its original depth. 

Besides the method of construction, the chief characteristic of this 
system of filtration is the slow rate of operation, usually not exceeding 
2 or 3 million gallons per acre per day. On this account these filters 
are often called slow sand filters; although they are also denominated 
European filters, English filters, and otherwise. The name “sand 
filter ’ ’ is, however, sufficiently distinctive and will be used in this work. 

The chief features to consider in this form of filter are the proper 
construction of sand-bed and drains, the rate of filtration and its regu¬ 
lation, the loss of head, cleaning of beds, washing of sand, and the 
control of the operation by bacteriological tests. 

487. General Results of Filtration.—In filtering water through a 
sand filter the main improvement to be noted is in the removal of the 
suspended matter. Even the color of a peaty water may be somewhat 
lessened, but that portion of the color due to matter in solution is not 
so readily removed by filtration. 

With respect to the elimination of bacteria and other micro-organ¬ 
isms, the results are so startling that it has been a question for a long 
time how to explain them. 

488. Bacterial Results.—Since the introduction of bacteriological 
methods, it has become possible to study the action of filters from an 
entirely new viewpoint. When cultures are made from the raw water 
and from the effluent of a properly operated sand-filter, a very great 
reduction in the number of bacteria is to be noted. The following 
summary of data compiled by Hazen * from the results of examinations 
made on the Lawrence City filter, which uses the polluted Merrimack 
River water, well illustrates the degree of purification. 

NO. OF BACTERIA PER C.C. 


Raw water. 

Filtered water. 

1894. 

10,417 
. 176 

1895. 

11,hi 

121 

1896. 

7,108 

91 

1897. 

10,360 

61 

189S. 

4.850 

46 

Efficiency of purification (per cent). 

* 

. 98.31 

98.91 

98.72 

99.41 

98-95 


The efficiency of the Berlin filters is likewise as marked. The fol¬ 
lowing results of Plagge and Proskauer t show the number of bacteria 
in the filtered water. 


* Filtration of Public Water-supplies, p. 106. 
f Zeitf. Hyg ., 1887, 11. p. 458. 












THEORY AND EFFICIENCY OF FILTRATION. 


423 


BACTERIAL CONTENT OF WATER FROM BERLIN FILTERS. 


Bacterial Content per c.c. 

Percentage Distribution. 

Stralau Filters. 

Tegel Filters. 

More than 1000. 

7 

2 

200 to IOOO. 

4 

7 

100 to 200. 

16 

9 

0 to 100 . 

72 

81 


489. Chemical Results. —The view that has generally prevailed as 
to the extent of chemical purification in filtration has bedn that practi¬ 
cally no improvement occurred in the water, owing to the fact that most 
of the substances that are determined chemically are in solution rather 
than in suspension, and could therefore pass through the filter. The 
work of the Lawrence, Mass., station shows, however, a very consider¬ 
able improvement in the water after filtration. Naturally all suspended 
matter is removed and quite a large though variable amount of soluble 
material, as well as some coloring matter, a condition shown in the 
following table: 

PERCENTAGE OF MATTER REMOVED BY FILTRATION AT LAWRENCE STATION, 

1894. 1895. 

Per cent. Per cent. 


Color. 43 30 

Albuminoid ammonia. 55 52 

Oxygen consumed.44 26 


THEORY AND EFFICIENCY OF FILTRATION. 

490. Theory of Filtration. —When working under favorable condi¬ 
tions, a sand filter will remove very nearly all of the bacteria originally 
present in the water. At first glance, it might be thought that this 
filtration process was merely a mechanical one, a straining out of the 
suspended particles by the sand layers. 

491. Inadequacy of Mechanical Explanations. —There are various 
reasons why such an explanation is not wholly satisfactory, although 
undoubtedly the mechanical theory is effective in part. If the process 
was purely mechanical, the filtered water should be as good at one 
time as another, but such is not usually the case. When a sand filter 
is first installed, the filtrate is much richer in germ life than it is later. 
As it increases in age, it becomes more efficient, showing that some 
other factor than purely mechanical removal, functions in the process. 
Then, too, the pore-spaces between the sand particles are sufficiently 
















424 


SAND FILTRATION. 


large to permit objects as small as the bacteria to pass through. The 
fact that they do not filter through in any considerable quantities indi¬ 
cates other than a mere mechanical removal. If the mechanical theory 
were correct, a variation in the fineness of the sand would in a measure 
affect the efficiency of the process, but, within the limits ordinarily 
employed, the difference in results due to variation in size of sand grain 
is very slight. The lack of relation between the number of bacteria in 
the affluent and effluent is also against a mechanical explanation. The 
following figures from different plants show a wide range in number of 
bacteria in affluent, a relation not to be recognized in the effluent. 



Number of Bacteria per c.c. 

Affluent. 

Effluent. 

T .ond on. 

800-igOO 

4400-7980 

58-237 

35-92 

22-52 

21-33 

Berlin. 

Zurich.. 



492. Inadequacy of Chemical Explanations.—The chemical changes 
that are to be noted in filtration are of such a nature that it is hardly 
conceivable that a satisfactory explanation of the phenomena of filtra¬ 
tion will rest upon a chemical basis. Generally there is some oxidation 
of the organic matter, as is shown by the reduction in “oxygen con¬ 
sumed.” Most of the improvement, however, in the chemical condi¬ 
tion of a water is occasioned not by purely chemical changes, but is • 
due to the action of the living organisms present in the filter. 

493. Biological Explanation.—As previously noted, a filter improves 
in efficiency as it grows older until it finally reaches a point where 
the flow of water through the same is so small as to necessitate clean¬ 
ing, a process technically known as scraping. But even after cleaning, 
the results obtained are better with filters long established than with 
new ones. With the improvement in the bacterial content of the 
effluent, a marked change occurs in the character of the sand, particu¬ 
larly in the upper layers. 

Naturally the suspended matter in the water, apparent turbidity as 
well as bacteria, is intercepted for the most part at the surface of the 
filter. Where there is an appreciable amount of these substances held 
in suspension in the water, a layer is quickly formed on the surface that 
quite changes the nature of the sand. Generally the coating is slimy 
and gelatinous, and to it has been ascribed the filtering power of a sand 













THEORY AND EFFICIENCY OF FILTRATION. 


425 


filter. This layer also forms, although more slowly, in waters that are 
relatively deficient in suspended matter, at least where particles are not 
sufficiently numerous to cause turbidity. When critically examined it 
is found to contain inorganic matter, as silt of all kinds, organic sub¬ 
stances, as bacteria, algae, diatoms, and amorphous material. 

While this jelly-like deposit is forming at the surface there is also 
an appreciable action of a similar nature going on in the depth of the 
filter. In this case the formation of this substance is produced by 
living causes, organic instead of inorganic matter, therefore, predomi¬ 
nating in its composition. This is due to the growth of the bacteria 
derived from the sand and water, the slimy matter being formed by 
the cells themselves and the exudation from the same. This organic 
matter accumulates more readily in summer than in winter, because of 
the more favorable growth conditions. 

While a casual examination of the sand layers will show in a general 
way the distribution of the organic matter, a bacterial study demon¬ 
strates the presence of the organisms in the body of the filter, but they 
are accumulated in much larger numbers at or near the surface, as is 
evident from the following data gathered from die results of examina¬ 
tions of ten filters at Lawrence.* 

TABLE NO. 68. 

I 

EXAMINATION OF TEN FILTERS AT LAWRENCE AS TO ORGANIC CONTENT AND BACTERIA 

AT DIFFERENT DEPTHS OF THE SAND 1 AYER. 


Depth. 

Inches. 

Organic Nitrogen. 
Parts per 100,000 
by Weight. 

Bacteria. 

Per Gram. 

o-f 

20 

6,600,000 

I 

9-5 

1,940,000 

3 

6.4 

720,000 

6 

4-7 

300.000 

12 

4.0 

90,000 

24 

2-3 

47,000 

36 

1.6 

35,000 

48 

1.2 

29,000 

60 

1.2 

26,000 


494. Importance of Sediment Layer.—The accumulation at the sur¬ 
face of the filter has led to the view generally accepted by the German 
school that this surface sediment layer (Schmutzdecke of the Germans) 
is the chief agent in effective filtration. From the experiments con¬ 
ducted at various places in this country it is quite evident that too 


* Report Mass. Bd. of Health, 1894, p. 635. 


I 










426 


SAND FILTRATION. 


much emphasis has been put upon the filtering power of this layer,* as- 
is shown from the following facts: 

Waters so free from suspended matter as to show no turbidity form 
by bacterial growth, in a brief time, an organic slimy deposit in and 
on the sand, by the aid of which good effluents are produced. Waters 
containing much inorganic sediment may not develop enough organic 
slime to bind the mineral matter into a layer and so hold it on the 
surface. In such a case the inorganic solids are forced into the body 
of the filter, to the detriment of the efficiency of the same. Again, 
filters having a well-developed superficial sediment layer may have the 
continuity of the same broken if the surface of the filter-sand be 
exposed to the air. This peeling of the slimy surface-coat ought to 
disturb the efficiency of the filtrate if this layer was the sole effective 
agent in filtration, as has been generally claimed. But such is not the 
case as shown by the Lawrence tests. 

Still again, the removal of the upper layer of the sand that has 
become clogged through deposition of suspended matter from the water 
ought to invariably impair the efficiency of the filtration until a new 
layer is produced. As a matter of fact such results do not necessarily 
follow, although it should be said that this is the most critical period 
in the condition of the filter. The Massachusetts experiments often 
s)iow as good an effluent immediately after cleaning as before. Under 
the same auspices it has also been noted that filters often become more 
effective with age and long service. This has been shown particularly 
with medium coarse or coarse sands. The efficiency increased in one 
case (Filter i%d) as follows: t 


Year. 

Rate. 

Bacterial Efficiency. 

Gallons. 

Per cent. 

1893 

2,000,000 

96 75 

1894 

4,500,000 

98.97 

1895 

4,500,000 

99-57 


Notwithstanding the increase in rate and the diminution in depth of 
sand from 5 to 3 feet (due to scraping) in two years, the character of 

the effluent steadily improved. 

\ 

* Reinsch {Cent. f. Bakt ., 1894, xvi. p. 881) also emphasizes in the case of the 
Altona filters the importance of the thickness of the sand layer in comparison with 
the sediment layer. 

f Mass. Bd. Health, 1895, p. 511. 











THEORY AND EFFICIENCY OF FILTRATION. 


42 7 


These facts cannot well be explained on the theory that the effec¬ 
tive agent in filtration is merely the surface layer. They are readily 
explainable, however, if one considers that the bacterial growth in the 
body of the filter exerts a strong effect on the filtration process. The 
value of the denser surface layer should not, however, be entirely 
neglected, but the relative merits of the organic slime in the inner 
layers of the filter should not be overlooked. 

To recapitulate, the effective agent in filtration in sand filters is the 
organic slime in the filter-bed and the accumulated surface sediment 
layer, which is made up of both inorganic and organic constituents. 
A filter is therefore something more than a mere mechanical strainer, 
inasmuch as its efficiency rests largely upon biological causes. The 
sand itself acts as a mechanical support for these gelatinous films, 
holding them intact; for this reason a certain depth of sand is necessary 
to steady the action of the filter and prevent disturbance of this organic 
slime. 

495. Bacteria in the Effluent.—Where a slow sand filter is doing 
satisfactory work, the number of bacteria found in the effluent is on the 
average small, either when expressed absolutely or compared with the 
number originally present in the unfiltered water. A good deal of 
variation, however, exists even in the same supply when a continuous 
study is made for considerable periods of time. The following varia¬ 
tions, taken at random from the Berlin results, illustrate this point: 

Number of bacteria per c.c. in filtered water: 

28, 200, 1656, 54, 26, 1000, 36, 24, 167, 220, 34. 

This inevitable fluctuation becomes of some moment when filters 
are only examined at intervals. Where examined daily, these ab¬ 
normally high results are diminished in importance. 

496. Origin of Bacteria in Effluent.—It is of considerable impor¬ 
tance to determine the origin of the bacteria appearing in the effluent, 
especially as this figure is used in interpreting results of efficiency of 
filtration. When bacteriological methods were first introduced, it was 
assumed that the difference between the number in the water before 
and after filtration represented the number removed. This assumption 
is now known to be false. If a specific micro-organism, such as B. pro - 
digiosus, which does not possess the quality of developing in the body 
of the filter and under-drains, is applied in sterile water to the filter,* 


* In determining whether such bacteria have passed the filter, roll cultures in 
large bottles are made by coating the inner surface of the bottle with nutrient gela¬ 
tin. In this way there is much less danger of overlooking colonies where the 
organisms are only sparsely present. 



4 ' 2 $ 


SAND FILTRATION 


it is possible to determine with much greater accuracy the exact origin 
of the respective bacteria in the effluent. More recently* * the colon 
organism, B. coli communis , has been utilized in this work. The 
value of this organism lies in the fact that it is generally a regular 
accompaniment of polluted water, and therefore if it should appear in 
the effluent its presence is indicative of danger to some extent. 

The relative proportion which actually pass through a filter and 
those which develop in the under-drains will vary at different seasons 
of the year and under different conditions as to filtration. During the 
colder months, when the water is low, the number developing in the 
filter will be at a minimum. Increased rate of filtration will diminish 
the number per c.c. in the drains by more rapid flushing, while the 
higher velocity will tend to force a slightly larger number through the 
filter. Of the two classes of bacteria appearing in the effluent, those 
that develop in the drains and body of the filter are the least important. 
They are generally the distinctive water organisms that naturally grow 
in such a habitat. 

If the sand of a filter is sterilized by steam or by the addition of a 
chemical disinfectant, and the water allowed to filter through the same, 
it has been observed that the effluent often contains more bacteria than 
the unfiltered water. This is due to the rapid development of bacteria 
in the sterilized sand, there being enough organisms derived from the 
percolating water to seed the filter. In the “ cooked ” filter the con¬ 
ditions seem to favor very rapid growth. The high number in the 
effluent then in a case like this is not due to filtration through the filter 
as was formerly supposed. 

497. Efficiency of Filtration.—Since the introduction of bacterio¬ 
logical methods it has been customary to consider the ratio of the 
difference between the number of bacteria in the raw water and in the 
effluent, to the number of bacteria in the raw water, as an index of the 
efficiency of operation, and this number is frequently referred to as the 
bacterial efficiency .+ Inasmuch as the bacteria in the effluent includes 
those organisms of post-filtration origin as well as those that have found 
their way through the filter, this bacterial efficiency evidently does not 
represent accurately the number of bacteria removed from the water. 
To determine this factor, which has been called the bacterial purifica¬ 
tion, it is necessary to add some special form to the applied water, as 
B. prodigiosus or B. coli communis , and then determine its frequencv 
in the filtered water. The hygienic efficiency is the percentage removed 

» 

* Clark & Gage. Science , Mch. 23, 1900. 

\ Mass. Bd. of Health, 1894, p. 592. 





THEORY AND EFFICIENCY OF FILTRATION. 


429 


bv filtration of applied bacteria capable of producing disease. It does 
not necessarily follow because one organism is able to pass through a 
filter that all others will, so the hygienic efficiency and the bacterial 
purification may not correspond closely. These relations are brought 
out strikingly in the tests made on the Lawrence City filter,* which 
were as follows: 



Number of Cases 
of Typhoid in City. 

Bacterial 

Efficiency. 

Per cent. 

Percentage of 
Cases in which 

B. colt was found 
in 1 c.c. of Water. 

December, 1898. 

12 

92.2 

72 

January, 1899. 

59 

98.31 

54 

February, 1899. 

12 

98.17 

62 

March, 1899. 

9 

99.89 

8 


Under ordinary working conditions, the germ content of the 
effluent should be reduced to the lowest possible terms. The German 
standard calls for an effluent with not to exceed 100 bacteria per c.c. 
when cultures are grown in gelatin for two days, but as a matter of fact 
this number is frequently exceeded even in good working filters, 
although the average number is usually below this limit. Generally 
speaking, the efficiency when expressed in percentage of number 
present in raw water ranges from 98 to 99 per cent, or above. In the 
case of filters using quiescent waters as sources of supply, as for 
instance in the case of Zurich, where the number of bacteria in the 
applied water is low (50 to 250), the percentage of bacterial efficiency 
is of course reduced. Where the source of supply is from running 
streams, as in the majority of cases in Germany, the bacterial content 
of the raw water is much higher, and consequently the percentage 
removed is much greater, f The efficiency of filtration is also much 
affected by variation in working conditions, as by a fluctuation in rate 
or by scraping the surface of filter. Formation of ice on uncovered 
filters is also detrimental. 

498, Passage of Bacteria Confirmed by Disease Outbreaks.—The pre¬ 
ceding experimentally controlled work can also be substantiated by 
observations made on the practical working of filters in relation to 
disease production. Between the years 1886 and 1893 several out¬ 
breaks of typhoid fever occurred in Altona, and in 1891 a marked 
epidemic in Berlin. The distribution of disease in these two cases was 

* Clark & Gage. Science, Mch. 23, 1900. 

f Pannwitz, Arb. a. d. Kais. Gesundheitsamte, 1898, xiv. p. 153. 




















45 ° SAND FILTRATION. 

such that it was evident that the same had been disseminated by the 
water-supply. In Altona these outbreaks invariably followed similar 
epidemics in Hamburg. In Berlin the case was strikingly emphasized, 
because the outbreak was confined to the region supplied by the 
Stralau (open) filters. At that time no search was made for the 
typhoid germ, but later in 1894, Losener* found the typhoid organism 
in the tap-water in this district, a discovery that was confirmed by 
Eisner, f During the cholera scourge in Germany in 1892-3 the 
cholera organism appeared in the filtered water of at least four cities.;}; 
It should, however, be noted that in these cases the filters were not in 
proper working conditions, on account of the presence of ice. With 
properly protected filters', carefully controlled, these outbreaks would 
probably not have occurred. 

Evidence such as the above indicates that it is possible for even 
disease bacteria to find their way through filters that are under actual 
working conditions. They are apt to do this more especially at times 
of stress as when the filter is frozen or new. Under normal operating 
conditions, the passage of disease-producing bacteria does not in all 
probability occur. 

These facts teach us that a sand filter is not by any means disease- 
proof. If improperly managed, it is possible that typhoid or cholera 
organisms may pass its layers. It is therefore an imperfect means of 
purification, but, as Frankel has well said, it is the best imperfect 
method that has yet been devised. 

499. Death-rates as Measures of Efficiency. —While the common 
method of expressing the efficiency of any filter is to measure it by the 
bacteria appearing in the effluent, either expressed absolutely or in 
terms of percentage apparently removed, still, after all, the effect on the 
death-rate or the case-rate of water-borne diseases is the crucial test of 
efficiency. Ordinarily this is not used because it has but little value 
until sufficient time has elapsed to overcome inevitable fluctuations, but 
as a final test of the work performed it is the court of last resort. 
This method has now been applied sufficiently long and under diverse 
conditions, so that the conclusions drawn ought to carry some weight. 
Where statistics are comparable, they invariably show a diminution in 
death-rate that is sometimes so marked as to be astonishing. Since 
the introduction of the method of sand filtration into Lawrence, Mass., 
a city that formerly used the polluted Merrimack River water, the 

* Arbeit, a. d. k. Gesundheitsamte, xi. p. 240. 

f Zeit. f. Hyg., xxi. p. 30. 

\ Frankel, C. Hyg. Rund., 1896, VI. p. 3. 




RA TE OF F1L TRA TION. 


43 t 

typhoid rates have been reduced nearly 90 per cent. In Hamburg the 
death-rate from typhoid was diminished by the installation of the filter 
over 70 per cent. Th*e most striking instance on record is the classic 
example of the protection afforded to the city of Altona in the summer 
of 1892, while its sister city, Hamburg, was striken with cholera 
(216). Numerous European cities that use this system are thus able 
to utilize surface-waters of doubtful purity, and by treating them in 
this way to insure a safe supply. 

\ 

CONSTRUCTION AND OPERATION. 

500. Rate of Filtration.—In the design of a filter-plant the first 
question to be settled is the rate of filtration which shall be adopted. 
The higher the rate the less the area required and hence the less will 
be the first cost; but the cost of operation is not greatly affected by the 
rate, so that the economy of high rates is not as great as it might 
appear at first sight. 

Rates of filtration are in this country usually stated in terms of 
gallons per acre per day or per hour, and on the Continent in meters 
depth of water per day or per hour.* 

501. Rates Used in European Practice. — The experience of Euro¬ 
pean works has resulted in the adoption of a rate, for most places, of 
between 2 and 3 million gallons per acre per day. This is materially 
less than the rate of 3.9 millions mentioned by Kirkwood as being the 
average in 1866, and denotes a marked change in practice since that 
time. 

The Hamburg works, completed in 1893, were designed on a basis 
of 1.6 millions. At Berlin the standard rate is about 2.6 millions. 
At London the average rate of all filters is about 1.8 million gallons 
per acre per day, but some companies use as high as 2.5 millions. 
Rates considerably higher than these are used in a few places, notably 
at Zurich, where a rate of nearly 8 millions is used with satisfactory 
results, but here the unfiltered water is very clear and contains but a 
few hundred bacteria per c.c. 

As a general statement 100 mm. per hour (equivalent to 2.57 
million gallons per acre per day) is considered by German authorities 
as a standard maximum rate. English engineers favor a slightly 
greater rate of 8 to 12 feet per day, or 2.6 to 3.9 million gallons per 
acre. 


* One meter per day is equal to 1.07 million gallons per acre per day ; one foot 
per day equals 0.326 million gallons per acre per day. 






432 


SAND FILTRATION. 


502. Effect of Rate on Efficiency. — The long experience of European 
works, resulting in the adoption of the rates given above, is very 
strong evidence that higher rates are undesirable. The decreased 
efficiency with increased rate has been directly shown in important ex¬ 
perimental studies by Piefke* * * § at Berlin. From these trials he recom¬ 
mended as low as 1.28 million gallons per acre daily as a safe maximum 
rate, but more recently he has used as high as 2.57 million gallons. 

It is undoubtedly true that high rates of filtration will give less 
efficiency than low rates when the difference is very great, but much 
evidence is available which indicates that, under certain conditions, no 
perceptible decrease in efficiency will result from a considerable increase 
in rate beyond the standard rates mentioned above. Experiments by 
Kiimmel at Altona on Elbe water, with rates of 4, 8, and 16 feet per 
day (1.3, 2.6, and 5.2 million gallons per acre), showed equally good 
results.t At Zurich, rates of from 4.4 to 21.5 million gallons per acre 
per day likewise gave equally good results. The latter experiments 
are not, however, especially significant for normal conditions on 
account of the extremely clear water and very low germ content. X 

The most important experiments in this direction are those which 
have been carried out by the Massachusetts Board of Health at 
Lawrence, Mass., on the Merrimack River water. This water is not 
often very turbid, but is badly polluted by sewage. It contains on the 
average about 0.2 parts per million of albuminoid ammonia. In 1892 
the results obtained on filters, the majority of which had been in opera¬ 
tion but six or eight months, indicated that the efficiency § decreased 
slightly with increase in rate, even for rates as low as o. 5 to 3 million 
gallons per acre daily. In 1893, with older filters, the influence of rate 
was not so apparent, but high rates were not as yet used. In 1894, 
rates of 5 to 10 million gallons and over were used with several of the 
filters, with satisfactory results “from those filters which had been in 
operation for a considerable period.” The bacterial efficiency in these 
cases was fully 99 per cent. With such high rates, however, the effect 
of scraping was more marked than with low rates. Regarding rates in 
practice, the following statement is made: [ “Experience during the 
past ten years with ten different filters which have been in operation at 
rates of 5 million gallons or more per acre daily leads us to the ccn- 


* Jour. f. Gasbel. u. Wasservers ., 1891, pp. 208, 228. 

f Trans. Am. Soc. C. E., 1893, xxx. p. 333. 

X Proc. Inst. C. E.. cxl. p. 280. 

§ Determined by the percentage of B. prodigiosus that passed the filters. 
| Mass. Bd. Health, 1894, p. 606. 





RA TE OF FIL TEA TION. 


433 


elusion that, with conditions substantially equivalent to those at 
Lawrence, the above-mentioned rate may be safely adopted in practice 
and yield an effluent of satisfactory quality after the first or second 
month of operation. ’ ’ These conclusions are further substantiated in 
the report for 1895, entirely satisfactory results having been obtained 
with rates of 5 to 7 million gallons. 

503. Rate to be Adopted. — In view of the results obtained above 
and the statements of the Board based on many years of experimenta¬ 
tion, it would appear that rates materially higher than those used 
abroad could be adopted with safety. In the Albany plant Mr. Hazen 
assumed a rate of 3 million gallons, but the plant has already been 
operated at times at a rate of 4 million with good results. A rate of 
3 million gallons has also been recommended by Mr. G. W. Fuller for 
a filter-plant at Cincinnati, his experiments showing that a rate as high 
as 4 million gave as good results as a lower rate, and with a coagulant 
5 millions.* 

A conservative course should unquestionably be followed in using 
higher rates than those established by foreign experience, and probably 
3 or 4 million gallons is as high as it would in general be advisable to 
go in the design of a new plant. If subsequent operation shows that 
a higher rate can be adopted with efficiency and economy, the fact can 
be taken advantage of as the demand for water increases. It should 
not be overlooked that there may be cases, as at Zurich, where, with 
a moderately polluted water, all the practical benefits of filtration can 
be secured at rates much higher than are usually employed. Each 
case demands independent consideration in order that the best and 
most economical solution may be arrived at. 

504. Uniform Rate Desirable. — Sudden changes of rate are apt to 
produce disturbances in the filter and to give a reduced efficiency. 
The Lawrence experiments on this point show that for a moderate 
increase in rate of 10 or 20 per cent the effect is inappreciable, but 
that a large reduction in efficiency is caused by an increase in rate of 
50 per cent. Marked reductions in rate followed by a return to the 
normal had little effect. It was also found that filters most sensitive 
to such changes were those of shallow depth, those ol coarse sand, and 
those that had been but a short time in operation. In practice, 
absolute uniformity of operation is unnecessary, but sudden changes in 
rate should be avoided, and especially any large increase above the 

normal. 


* Report on Water Purification at Cincinnati, p. 186. 






434 


SAND FILTRATION. 


505. Capacity.—The standard rate having been determined, the 
required net working capacity will be equal to the maximum rate of 
delivery divided by the assumed rate of filtration. To economize area 
and to avoid rapid changes in rate, a clear-water reservoir should be 
provided. The best size for this will depend on local conditions, but 
it will usually be desirable to have it of sufficient capacity to equalize 
the demand throughout the day. It will then be necessary to vary the 
rate of filtration only to accord with the daily variations in consumption 
(see Art. 527). In Chapter II it was shown that the maximum daily 
rate of consumption is likely to be about 1 50 per cent of the average, 
and with a clear-water reservoir of the capacity mentioned above the 
filters must be designed to deliver at this maximum daily rate. If the 
reservoir has a less capacity, then the maximum rate of delivery of the 
filters will be correspondingly increased. Occasional high rates of 
consumption and extraordinary demands may be provided for by the 
use of a rate of filtration somewhat higher than the standard adopted. 

In addition to the area as above found, a reserve area for cleaning 
must be provided. For small works this will be one bed; for works 
containing several beds it will be necessary to allow one bed for each 
5 to 10 beds, depending on the frequency of scraping and the time 
required for putting a filter into operation after cleaning. 

506. Number and Size of Beds.—The proper size of beds is chiefly a 
question of economical construction. The larger the beds the less the 
cost per acre, but the greater will be the area out of service in the one 
or more reserve beds. Ordinarily the size for a considerable number of 
beds is from 1 to 1.5 acres for open beds, and from .4 to .8 acres for 
covered beds. For small total areas of .5 to 1 acre three beds would 
ordinarily be used, and for still smaller areas two beds. The 
economical number can in any case be determined by comparative 
estimates, but some assistance may be had by the following mathe- ; 
matical analysis. 

The cost of a filter may roughly be estimated as made up of two 
items: (1) a portion proportional to the area, which would include cost 
of bottom, filling, small drains, cover, and the end walls, we will say 
(basins assumed rectangular and placed side by side); and (2) a portion 
nearly independent of the size, such as cost of piping, valves, valve- 
chamber, division walls, etc. Let c — amount of the first portion per 
acre, and C — the latter portion per filter. If q — area of one filter, 
n — number of filters, and A = total net area required, then if one 
filter is to be held in reserve, 

A 

n =-f- 1 

<1 


(0 



NUMBER AND SIZE OF BEDS . 


435 



X 


o 


W 

U 

6 
o 
c n 

a 

< 

«5 

a 

cfl 


a 

o 









































































436 


SAND FILTRATION . 


The total cost is 


K — Cn -j- cwq , ... 

= + I )+^7 +I ) 


• • • 


A 

= — + C + cA + c S , 
(7 


We then have —r = — 


dK 

dq q 

whence for a minimum cost 


—r + 


- 


( 2 ) 


• • • * 


( 3 ) 






( 4 ) 


that is, the economical capacity is proportional to ^ and to 


t/f- 


The larger the value of c the smaller is q , and hence for covered beds 

C 

q will be smaller than for open beds. The value of - will hardly be 


larger than -J- or less than giving a value of q = £ VA to £ VA* 
Thus when A = i acre, the capacity would be J to acre, giving 3 
or 4 beds; for A = 4 acres, q — £ to -§, giving 6 to 8 beds; and for 
A — 9 acres, q — § to 1 acre, giving 9 to 12 beds, etc. When the 
number becomes so large as to require two beds to be held in reserve 
the size will no longer increase with the area. Sizes considerably 
larger than 1 acre have been used, such as 1.9 acres at Hamburg, but 
they will hardly be economical unless the cost of valves, valve-cham¬ 
bers, and the like, is very high compared to the cost of the sand bed. 

507. General Construction.—Filter-beds are usually rectangular in 
form and arranged side by side in one or two rows according to the 
number. The shape of the area available often determines this point, 
but otherwise a convenient arrangement is to place them in two rows 
with a space between for sand-washing, etc., and to have valve-cham¬ 
bers facing this central passageway, as illustrated by the Albany plant 
(Fig. 120). A single row would be more economical of masonry, but 
would require more piping. 

A large number of basins may be divided into groups and arranged 
in the above manner. 

The economical proportions for rectangular beds arranged side by 
side is approximately given by the formula derived on page 414 for 






GENERAL CONSTRUCTION. 


437 


b 71 —I— i 

settling-basins. It is - = — , where b = width, 

a 27 i 

7 i = number of beds in a row. This assumes the cost 


a = length, and 
per lineal foot of 



interior and exterior walls equal, which is approximately true. A 
larger cost of interior walls will tend to increase b and vice ve7'sa. 
























































































































43 § 


SAND FILTRATION. 


The cost of the large central drain running lengthwise of the bed will 
also tend to increase b , while the expense of exterior piping will tend 
to reduce it. 

In general construction a filter-basin is built in a way similar to 
small distributing-reservoirs. (See Chapter XXVII.) Earth embank¬ 
ments for the sides are cheaper than masonry walls, but require more 
ground. If the filters are covered, masonry walls are usually employed. 
Particular care must be taken to render the basin water-tight, both on 



Fig. 122. — Interior View ; Albany Filters. 

(From Trans. Am. Soc. C. E., vol. xliii.) 


the bottom and at the sides. Cracks in division walls are likely to 
admit unfiltered water to the under-drains and should be especially 
guarded against. 

The depth of open filters is made only sufficient to contain the 
necessary depth of filtering materials and water, as explained subse¬ 
quently, and still have a margin of 2 or 3 feet from the water-surface 
to top of the embankment. This will give a total depth of 9 or 10 feet. 
In closed filters the distance from top of sand to cover must be sufficient 

to give head-room for workmen when cleaning the filter, a distance of 
about 6 feet. 

Covers for filters are constructed of the same general form and 
arrangement as described in Chapter XXVII. Masonry or concrete 
vaulting is usually employed, although wood has been used; but the 
















COVERING OF FILTERS. 


439 


latter does not afford as good a protection from freezing or from summer 
heat. Admission for workmen is provided by a gangway leading from 
an opening afe a point where the vaulting is raised. Walls and piers 
should be built with small offsets near the bottom in order to insure 
good filtration at that point. The covered filter at Albany is illustrated 
in big. 122. Groined arches of concrete were there used. Fig. 123 
shows a section through the gangway of a filter and also the general 
method of construction. 



Earth Covermi 


Water Level 


'Sand Run Tracks 


Underdrain 


Gravel 




Mam Underdrain 



Fig. 123. —General Construction of a Covered Filter. 

(From Report on the Water-supply of Philadelphia, 1899.) 

508. Necessity for Covering Filters. —Since the cost of covers 
amounts to about one-third of the total cost of filters, the question of 
open versus closed filters is a very important one. The principal 
reason for covering filters is to avoid the difficulties connected with the 
operation of open filters in winter. To clean filters when covered with 
ice is a troublesome and expensive operation, requiring the removal of 
the ice or the use of special methods giving inferior results. If the 
filters are drained for cleaning, trouble also arises from the freezing of 
the sand. The cleaning of beds is thus not likely to be done as 
promptly as desirable, and the result of winter operation will be a 
decreased effective area and a lowered efficiency. 

At Berlin all beds are now covered. At Hamburg open filters are 
used. Ice forms there, however, to a thickness of io or 12 inches and 
causes considerable trouble in cleaning. In England filters are not 
covered and little trouble is experienced, but the winters are quite 
mild, the mean January temperature at London being about 38°. At 





























































































































440 


SAND FILTRATION. 


Poughkeepsie, N. Y., and at Lawrence, Mass., a large part of the 
expense for cleaning is for the removal of ice in winter. Whether 
covers should be used depends upon the extent to which ice will form, 
the frequency of the occurrence of thaws which will enable a filter to 
be properly cleaned, and the length of time between cleanings as 
determined by the character of the water. From wide observations 
Mr. Hazen * proposes as a general rule that covers should be used 
where the average January temperature is below 32 0 . This includes 
the area north of a line passing through St. Louis, Cincinnati, Pitts¬ 
burg, and Philadelphia. 

Another very considerable advantage of covered filters in some 
places is in the prevention of the growth of algae, and thereby reducing 
the frequency of cleaning. At Zurich both open and closed filters 
were for a time in use. The number of days between scrapings, was. 
on the average, for 1891 and 1892, as follows :f 

1891. 1892. 

Covered filters. 37 36 

Open filters. 28 23 

At Poughkeepsie much trouble is also experienced from the growth of 
algae in the open filters there used. 

509. Effect of Cold Weather on Efficiency of Filtration. — The 
- reduced efficiency of open filters in winter is shown by the results of 
bacteriological analyses, but it is further substantiated by a consider¬ 
able number of disease epidemics that have broken out in the winter in 
cities supplied with filtered water. The coincidence of diminished 
bacterial efficiency and the appearance of a disease outbreak attributable 
to the water-supply leaves no doubt as to the possibility of pathogenic 
bacteria being able to pass the filter under certain conditions. 

In 1889 the effluent of the Stralau (uncovered) filters in Berlin 
contained on the average less than 100 bacteria per c.c., but in March 
of that year, at a time when the filter operations were interfered with 
through the action of cold weather, the number rose to 3 or 4 thousand. 
Coincident with this change occurred a typhoid epidemic, and also 
one of dysentery, that were limited to the Stralau district, while that 
portion of the city supplied from the Tegel filters remained free from 
both diseases. The history of the open filters at Altona is also similar. 
Outbreaks of typhoid have occurred explosively at Altona in the winters 
of 1886, 1887, 1888, 1891, and 1892, and Reincke has traced these 
to the imperfect operation of the filters during cold weather. It is 

* Filtration of Public Water-supplies, p. 12. 
f Report Zurich Water-works, i8g2, p. 27. 







THE FILTERING SAND. 


441 


significant that in almost every case these outbreaks were preceded by 
similar epidemics in Hamburg, and furthermore that they only 
occurred in Altona during the winter, when the action of the filters was 
impaired by frost. In the typhoid outbreak that occurred in the early 
part of 1891, Wallichs* had noted a sudden increase from a normal of 
less than 100 bacteria per c.c. to 2615. The small winter outbreak of 
cholera that occurred in Altona in 1893 Koch was able to trace to the 
imperfect operation of a single filter. 

510. The Filtering Sand. —In selecting a sand for filtering purposes 
the important properties are its size and uniformity of grain, the pres¬ 
ence or absence of fine material and organic matter, and its chemical 
composition. 

511. Mechanical Analysis .—The particles of any given sand vary 
much in size, but as regards the size of the interstices and the percola¬ 
tion of water, it is obvious that the size of the finer particles rather than 
the coarser determines its effective size. From experiments by the 
Massachusetts Board of Health it was found that the measure which 
would best represent the size of the sand is such a size of grain that 10 
per cent by weight of the sand is finer than this size, and 90 per cent is 
coarser. This size is denominated the effective size and is usually stated 
in millimeters. The average size is much larger. As a measure of 
the uniformity, the above authorities have adopted the ratio of the size 
of grain which has 60 per cent finer than itself, to the size which has 
10 per cent finer (the effective size). This ratio is called the uniformity 
coefficient; the smaller the coefficient the more uniform the material. 
The above terms or measures have been quite generally adopted as the 
standard. 

Methods of analysis of size are fully described by Mr. Hazen in the 
Massachusetts Report for 1892, page 541,t and in his work on “ Filtra¬ 
tion of Water-supplies.” Gravel is separated by hand-picking into 
several sizes, and the average size of each is determined by weighing. 
Sand is separated by sets of sieves with meshes ranging from 2 to 200 
per inch. The proportion of sand or gravel finer than each particular 
size is then plotted and the effective size, or the size corresponding to 
the 10 per cent proportion, is readily found. Care must be taken to 
have the sand thoroughly dry before sifting. 

The separation size of any particular sieve is found by Mr. Hazen 
by determining the average diameter of the very last particles to pass 
the sieve. To compute this, the weight and specific gravity of a known 

* Deutsche med. Wochenschrift, 1891, No. 25. 

+ See also Eng. Record, 1897, xxxv. p. 163. 







442 


SAND FILTRATION. 


number of such particles is determined and the grains calculated as 
spheres. The actual size of mesh is irregular, and the number of 
meshes per inch is not to be relied upon as a measure of size. 

For particles finer than o. i mm. (corresponding to a sieve with 
about 200 meshes per inch) the method of elutriation is used. In this 
process, 3 grams of sand are placed in a beaker 90 mm. high and hold¬ 
ing about 230 c.c., and the beaker is then filled with distilled water at 
20° C. (68° F.). The water and sand are thoroughly mixed and 
allowed to stand 15 seconds, and the water is then decanted. This is 
repeated twice and the sand is then weighed. Experiments show that 
this sand can be considered as greater than 0.08 mm. in size. The 
decanted sand is then treated in a similar way, with one minute for set¬ 
tling, and the sand which settles calculated as greater than 0.04 mm. sand. 
The amount of the portion below 0.04 mm. is estimated by difference. 

512. Selection of Sand. — Experiments show that very fine sand is 
considerably more efficient in removing bacteria than ordinary or coarse 
sand, but within the ordinary limits of size (0.2 to0.4 mm.) the Lawrence 
experiments indicate but little difference in efficiency. The finer 
sands, however, cause a steadier action and prevent disturbances due 
to scraping; they also cause a greater loss of head in the filter, and so 
make the action more uniform over the filter area. On the other hand, 
fine sand becomes clogged sooner than coarse and involves therefore 
more expense in cleaning. For waters containing very fine sediment, 
coarse filters are likely to become clogged to a considerable depth, 
requiring the removal of too thick a surface layer. 

In practice the size of sand used varies from about 0.2 mm. for 
some of the Holland dune sands to about 0.4 mm., averaging about 
0.35.* It is desirable that a sand be fairly uniform in grain. If the 
particles vary greatly in size, it will be difficult to wash, and in fact will 
have much of the finer particles removed in the process, thus increasing 
the effective size. It is especially important that the sand should be 
of the same grade in all parts of the same filter in order that the frictional 
resistance, and therefore the rate of filtration, shall be uniform. Frequent 
analyses should be made as the sand is delivered at the works. 

Regarding other requirements, the sand should be free from clay, 
and if necessary it should be washed. The chemical composition is 
also important, as a sand containing a considerable amount of lime will 
increase the hardness of the water. It has also been found that the 
presence of aluminous and calcareous material increases very materially 
the resistance to the flow of water. + 

* See analyses of sand from many filters in Hazen’s “ Filtration of Water- 
supplies.” f Mass. Report, 1894, p. 757. 






FRICTION IN THE SAND LA YER. 


443 


The specifications for the sand for the Albany filter-plant, Allen Hazen, 
Mem. Am. Soc. C. E , engineer, were as follows : 

“The filter sand shall be clean river, beach, or bank sand, with either 
sharp 01 rounded grains. It shall be entirely free from clay, dust, or organic 
impurities, and shall, it necessary, be washed to remove such materials from 
it. I he grains shall all of them be of hard material, which will not disinte¬ 
grate, and shall be of the following diameters: Not more than i per cent by 
weight less than 0.13 mm., nor more than 10 per cent less than 0.27 mm.; 
at least 10 per cent by weight shall be less than 0.36 mm., and at least 70 
per cent by weight shall be less than 1 mm., and no particles shall be 
more than 5 mm. in diameter. The diameters of the sand grains will be 
computed as the diameters of spheres of equal volume. The sand shall not 
contain more than 2 per cent, by weight, of lime and magnesia taken together 
and calculated as carbonates/’ 

513. Friction in the Sand Layer.—The results of experiments by the 
Massachusetts Board on flow of water through sand have already been 
given on page 91, in connection with the flow of ground-water. The 
formula is 





where V = velocity of water in meters daily in a solid column; 
c = a coefficient, equal to about 1000; 
d — effective size of sand; 
h = head causing flow; 

/ = depth of sand layer; and 
t = temperature in degrees Fahrenheit. 

Later experiments with compacted sand in old filters showed the 
value of c to be about 800 for comparatively uniform sands. Using 
this value of c , the following table of losses of head, or values of has 
been calculated for a filter 1 foot thick. 


TABLE NO. 69 . 

FRICTIONAL HEAD IN FEET, IN COMPACTED SAND ONE FOOT THICK, AT A 

TEMPERATURE OF 50 ° F. 


Size of 


Rate of Filtration, Millions of Gallons per Acre per Day. 


Milli¬ 

meters. 

I 

13 

2 

2 $ 

3 

33 

4 

43 

5 

•15 

.052 

.078 

. 104 

.130 

•156 

• 

M 

OO 

to 

.208 

•234 

. 260 

.20 

.030 

•045 

.060 

•075 

.O9O 

. 105 

. 120 

•135 

.150 

.25 

.019 

.028 

.038 

.047 

.056 

.065 

•075 

.084 

.094 

•30 

.013 

.020 

.026 

•033 

•039 

.046 

.052 

.058 

.065 

•35 

.010 

.014 

.019 

.024 

.029 

•034 

.038 

•043 

.048 

.40 

.007 

.011 

.014 

.018 

.022 

.026 

.029 

•033 

•037 
































444 


SAND FILINA IVON. 


The effect of temperature on the resistance is very marked, the loss, 
of head at 40° being 20 per cent higher, at 6 o° about 14 per cent 
lower, and at yo° 25 per cent lower than the above figures. 

The loss of head in a freshly cleaned filter composed of a 0.30-mm. 
sand, 4 feet deep, and filtering at a rate of 3 million gallons per acre per 
day, will be, according to this table, approximately. 039X4— feet ’ 
or about 2 inches. In the winter it will be more and in the summer 
less. After a filter has been in use for some time after cleaning, the 
effect of clogging is of course to cause a loss of head many times. 


I I 


* § 
/X 

" .E 

Xi-3 >:?. 


c •§ 

O t 

Q > -i; 


-si 


2 a 
















I 1 N 11 11 -- 





M m \ \ - — 





y/A vA - - 





YAl. .Y: V :X 7 A. 



W A 

L 







777 Z 

777 , 

'//A 

m 

W/ 

A?////, 





ip 




10 

8' 


greater than these figures. 

514. Thickness of Sand Bed.—In the older filters great variations 
exist in the thickness of the several layers of sand and gravel, and in 

the depth of water on the filter. Fig. 
124 shows the make-up of many filters 
abroad and illustrates this lack of uni¬ 
formity. It will be seen that the thick¬ 
ness of sand is usually from 2 to 3 feet, 
e>- the gravel layer about the same, and 
the depth of water about 3 or 4 feet. 
In some filters a layer of fine sand is 
underlain by a thick layer of coarse. 

In designing a filter it should be 
noted that the sand forms the filtering 
medium; the gravel serves simply to 
collect the filtered water with little 
resistance to flow. There is no object 


mm 


4' 

2* 

0 

2* 

4 ' 

6' 

8‘ 

16. 


Great Britain & Ireland. 



Germany. Netherlands 

Fig. 124. —Make-up of Foreign Filters. 

(From Engineering News. vol. xxvm.) 


in having the main body ot sand of different sizes unless it happens that 








































































































































































ERA IN A GE S VS I 'EMS. 


44 5 


a sand of the fineness desired for the upper portion of the bed is expen¬ 
sive, in which case a coarser sand may be used for a considerable 
thickness next to the gravel. A fine sand should never be placed 
below a coarser one, as this will cause subsurface clogging. 

The original depth of sand must be sufficient to form an effective 
filter and, besides, to allow of several scrapings without the renewal of 
the sand. Inasmuch as the bacterial efficiency depends in part on the 
action which takes place in the body of the filter (Art. 494), and not 
exclusively at the surface, an increase in depth within certain limits will 
tend to increase the efficiency of the filter. The Imperial German, 
Board of Health requires as a minimum at least 12 inches, but in actual 
practice the beds are considerably thicker. The effect of deep beds is 
similar to that of fine sand in steadying the action of a filter, and it has 
been clearly shown by the Lawrence experiments that the operation of 
oeds 4 to 5 feet thick is not so much affected as that of beds 1 to 2 feet 
thick by such disturbances as variations in rate, scraping of beds, etc., 
although the results with perfectly uniform conditions are not materially 
different. The effect of depth is also very important in causing a more 
uniform action over tne entire bed of a freshly cleaned filter by minimiz¬ 
ing- the effect of frictional resistance in the under-drains. 

o 

For the foregoing reasons it would seem desirable to adopt a mini¬ 
mum thickness of at least 2 feet, and to make the bed originally 3 feet 
thick. In several filters recently constructed the original depth of sand 

is 4 feet. 

515. The Depth of Water on the Filter should be sufficient to enable 
the desired maximum head to be used without reducing the pressure 
in the filter below atmospheric; and as the resistance is nearly all at 
the surface of the sand, the depth must be about equal to the maximum 
head used. (Art. 520.) Certain experiments have shown that 
“negative heads ’* are likely to cause the liberation in the filtei of 
some of the air dissolved in the water and so cause disturbances. The 
depth must also be greater than the thickest ice likely to form. Beyond 
these limiting depths any increase serves only to increase the expense 

of construction. 

516. Drainage Systems.—To collect the filtered water a system of 
under-drains is necessary. The important points to be considered in 
its design are durability and freedom from derangement, and that the 
loss of head therein shall be small. The system of drains usually con ¬ 
sists of a large central drain running the length of the filter, and branch 
drains at right angles thereto placed at regular intervals, usually of 
8 to 12 feet. The central drain may be made either of large vitrified 


SAND FILTRATION. 


446 

pipe or of masonry 5 the branch drains are usually of 4~ to 8-inch round 

or special tile, laid with open joints. 

To avoid using a very large amount of gravel filling in older to form 
a level surface for the sand bed, the main drain should be sunk into the 
floor of the filter so that its top is no higher than the laterals. For the 
same reason the floor of the filter is sometimes made wavy in section 
and the laterals are placed in the depressions so formed. Various 
arrangements are illustrated in Figs. 125 to 128. 

To conduct the water to the lateral drains, coarse gravel an inch 
or two in diameter is filled about the drains and spread in a layer of 
6 inches or more in depth evenly over the floor of the filter, or, if the 
bottom of the filter is irregular, it may be arranged as shown in Fig. 
127. Above this coarse gravel are then placed three or four layers of 
finer gravel, each successive layer being finer in size, but not so fine as to 
settle into the previously laid layer. The last layer is made fine enough 
to support the sand. The thickness of these layers need be only 2 01 
3 inches if carefully laid, or just sufficient to insure that the next layer 
below is well covered. In many of the old filters as much as 3 or 4 
feet of gravel was used, with very large sizes at the bottom, but as it 
has little or no duty except to act as a drain, any depth above what is 
needed for this purpose only adds to the expense of construction. It 
will be seen that the frictional resistance in gravel only I or 2 inches 
in diameter is very small at the velocities which obtain. 

The gravel used should be carefully screened and, if dirty, washed. 
It is readily sized by revolving or fixed screens, using for this purpose 
three or four different sizes. The smallest should have about a -p^-inch 
mesh, and each larger size about double the size of mesh of the next pre¬ 
ceding. At Albany the sieves used were T 3 ^, f, 1, and 3 inches respec¬ 
tively, all of the gravel being required to pass through the 3-inch sieve. 

517, Special Arrangements .—In some cases, in place of lateral 
drains covered by a deep layer of gravel, a cellular floor is used. This 
may be made by laying brick flatwise, with narrow open joints, upon 
other brick placed at right angles thereto, an arrangement which 
requires but little gravel and occupies but little space in the filter. In 
other cases, drain-tile has been laid at right angles to the main drain 
so as to cover the entire bottom. Still other arrangements have been 
employed and various special tile used. The only office of the drainage 
system is to furnish a channel for the flow of the water with a certain 
minimum loss of head, and that arrangement should be used which will 
accomplish this in the most economical manner and leave a level bed 
for the sand layer. 


DRAINAGE SYSTEMS. 


4 47 


518, Examples. —Fig. 125 illustrates the drainage arrangement of the 
Hamburg beds. The filters have an area of 1.89 acres each. The central 
drain is 22 by 32 inches, with brick sides and masonry cover. The laterals 
are 6 inches wide and 7^ inches high, and are spaced about 30 feet Iipart. 
The gravel layer is 2 feet thick. * The proposed filters for Cincinnati | are 



Fig. 125. —Section of Hamburg Filter. 


d-si gned with an area of 2 acres each. Two main drains are provided with 
effiuent chambers at each end of each drain. Fig. 126 shows a section 
through the main drain and filter. The laterals are of vitrified salt-glazed 
tile, with butt-joints and flat bottoms. Inside dimensions are 6 inches wide 
by 8 inches high. They are spaced 11.8 feet apart. 



Fig. 126. —Section of Proposed Filter at Cincinnati. 

The arrangement of drains in the Albany plant is shown in Fig. 120, page 
435, and sections through a main drain and laterals in Fig. 127. The filter 
is covered, and a 6-inch lateral is laid in each space between the rows of piers. 
The drains are of vitrified pipe, the laterals being laid with open joints. 

Fig. 128 is a plan of bed and a section through the central drain of the 
new Zurich filter. The main drain is of concrete, and the laterals are of tile, 
laid over the entire floor.]; 

519. Loss of Head in the Drainage System.— The total loss of head 
in the filter is equal to the loss of head in the sand plus that in the 

* Meyer. Das Wasserwerks Hamburgs, p. 19. 

\ Report of the Engineer Commission, 1896. 

% Eng. Record , 1899, XXX ix. p 472 . 




































































44 8 


SAND FILTRATION . 


under-drains. That in the sand is uniform throughout the filter, but in 
the under-drains it varies from zero near the outlet to a maximum for 




Section through Lateral. 

Fig. 127.—Details of Drains, Albany Filter-beds. 
(From Trans. Am. Soc. C. E., vol. xliii.) 



Crawl. 


Adjustable Weir. " | j 

Overflow and Drain 

Effluent.S' 


Curved Iron Weir 
Regulating Apparatus. 
Vnflltertd Water. 


T* IMNSM KfiOSft 


Concrete 


Cnd View 
Special Brides. 


Concrete Bottom 
of niter. 


Fig. 128.—Filter-bed and Drain Details, Zurich. 

(From Engineering Record , vol. xxxix.) 

the most remote point. The rate of filtration will be proportional to 
the total head and therefore will vary in different parts of the bed. 


























































































DRAINAGE SYSTEMS. 


44Q 


The loss of head in the drains should be kept so low that with a clean 
filter the variation in the rate of filtration in different parts of the bed 
will not be excessive. A variation of 20 to 25 per cent would not be 
a serious matter, as the excess above the average would then be only 
10 or 12 per cent. Furthermore, this difference would occur for only 
•a short time after cleaning, for as a filter becomes clogged the relative 
difference in heads is much less. 

If we take, for example, a filter composed of .30 mm. sand, depth 
4 feet, rate of filtration 3 million gallons per acre per day, the loss of 
head due to the sand alone when the filter is clean will be about .039 
X 4 = .156 foot. If we allow a maximum loss of, say, one-fifth of this 
for the drains, or .031 foot, the total head will then vary from .156 to 
,187, and the rate of filtration will vary about 10 per cent above and 
10 per cent below the average. To keep the loss of head in the drains 
to this low limit requires the use of low velocities and relatively large 
pipes. 

The loss of head in drains according to Kutter’s formula is given 
in Table No. 70. The loss of head in gravel per foot of distance is 
approximately given in Table No. 71.* 


TABLE NO. 70 . 

FRICTIONAL HEAD IN DRAINS, IN FEET PER TOO FEET OF DRAIN. 


Discharge. 
Gallons per Day. 

Velocity. 

Feet 
per Sec, 

Diameter of Drain in Inches. 

4 

6 

8 

IO 

12 

15 

18 

20 

24 

30 

7ooX(diam.) 2 

.2 

.012 

.006 

.004 








1400“ “ 

•4 

.050 

.025 

.Ol6 

.Oil 

.009 

.006 

.005 

.004 

.003 

.002 

2 TCO “ “ 

.6 

•113 

•057 

.036 

.025 

. 019 

.014 

.011 

.009 

.007 

.005 

2800 “ “ 

.8 

. 202 

. IOI 

.064 

•045 

• 035 

.025 

.019 

.016 

.012 

.009 

35OO “ 

1.0 

•315 

.158 

. IOO 

.070 

• 054 

•039 

.030 

.025 

.019 

.014 


TABLE NO. 71 . 


FRICTIONAL HEAD TN GRAVEL PER FOOT OF DISTANCE. 


Rate of Flow. 
Gals, per Day 
per Square Foot 
of Cross-section 

Effective Size of Gravel in Millimeters. 

10 

20 

30 

40 

500 

.OOO35 

.00012 



IOOO 

.0007 

.00025 



2000 

.0014 

.0005 

.00025 


3000 

.0022 

.0008 

.00037 

.00025 


* Based on results of experiments of Mass. Bd. Health, Report for 1892, p. 555. 
















































45 ° 


SAND FILTRATION . 


The loss of head in the gravel can be kept low either by means of 
a thick layer, or by putting the drains close together. Wide spacing 
requires fewer drains, but larger sizes and more gravel. When the cost 
of drains and gravel is known, the most economical arrangement for a 
given loss of head can be determined by a few trials. 

Thus with a rate of 3 million gallons per acre per day (equal to 
about 75 gallons per square foot per day), and drains 20 feet apart, the 
total flow through each foot of width of gravel will be 10 X 75 = 75 ° 
gallons. With 6 inches of 20 mm. gravel the average flow per square 
foot will be 2 X 750 — 1500 gallons, and by the above table the loss 
of head is seen to be about .00037 foot P er foot. The average distance 
travelled is 5 feet, hence the total loss of head in the gravel will be 
.0018 foot. This is a very small loss and would usually be much 
smaller than necessary. A still thinner layer of gravel might therefore 
be used, or the drains placed farther apart. 

The maximum length of drain (main and lateral) for beds of one 
acre in area will be about 350 feet. If the total loss is to be kept down 
to, say, .03 foot, this will allow but about .008 foot per hundred feet in 
the drains. Inspection of Table No. 70 will show that it will be 
necessary to use velocities of .2 to .3 foot per second in laterals, and 
.6 to .8 foot in main drains. The necessary size for any given capacity 
is readily computed. The size of main drain should increase towards 
the outlet. In the above example, 6-inch laterals 20 feet apart would 
themselves consume about .023 foot of head, an amount too large where 
the total allowable loss is only .03 foot. Eight-inch drains 20 feet 
apart would use only .0035 foot, leaving about .026 foot for the main 
drain. This can then be made up of sizes varying from 12 to 3© 
inches. With thin beds of coarse sand the difficulty of maintaining 
uniform rates is evidently much increased. 

520. Maximum Total Loss of Head.—As a filter becomes clogged 
the head necessary to cause filtration at the assumed rate increases. 
By allowing the head to increase to a high figure the filter can be 
operated longer without scraping and so a saving in operation effected. 
On the other hand high losses of head require more pumping, a greater 
depth of filter, and have a detrimental effect in compacting the sand. 
It has also been thought that a high pressure would be detrimental in 
its effect on the surface film of the filter and would thus lead to 
decreased efficiency; consequently many of the late filters abroad are 
made with an available maximum head of only about 2 feet. This 
opinion has not been well confirmed. In fact the experiments of the 
Massachusetts Board show that heads of 70 inches, constantly used 


INLET-PIPES. 


451 


Indicator Post 



Ei.ios.a 


there, give substantially the same bacterial efficiency as lower heads. 
Many filters in use also operate under heads of 4 or 5 feet with good 
results, and there appears to be no good reason for using less than this. 
Much higher heads would probably not be economical. Results of 
operation and experiment show in some cases an increase in time 
between scraping proportional to the maximum head used, and in other 
cases the gain in time is much less proportionally than the increase 
in maximum loss of head. 

521. Inlet-pipes.—Water is admitted to the filter through a single 
branch main at about the level of the surface of the sand. The flow is 
usually controlled by a balanced 
valve operated by a float, so as to 
maintain the water in the filter at a 
constant level. A gate-valve is pro¬ 
vided in addition, to enable the water 
to be completely shut off at any time. 

Fig. 129 illustrates the float-valve 
used at Albany, while Fig. 130 shows 
in detail a somewhat different form 
designed by Mr. D. W. Mead for the 
filters at Rock Island, Ill. To avoid 
disturbing the sand as much as possible the water should flow upon the 
bed at a slow velocity, and a common arrangement is to provide a 
broad weir, as shown in Figs. 128 and 129, over which the water passes. 
On filling the filter after cleaning, it is necessary then to fill from below 
only slightly above the surface of the sand before turning on the 
unfiltered water. 

In place of providing a regulating-valve for each filter the influent 
pipes may all lead from a central regulating-well in which the water- 
level is maintained constant. Such an arrangement is suited to a 
compact group of small filters. 

522. Outlet-pipes and Apparatus for Regulating the Head.—If the 

water-level on the filter is kept constant, the rate of filtration must be 
regulated, as the filter becomes clogged, by lowering the water-level 
or reducing the pressure at the outlet. In the older filters no arrange¬ 
ment was provided for regulating each filter independently, but each 
was connected to the clear-water well by a short pipe fitted with an 
ordinary valve. The head on all filters was consequently always the 
»ame, except as it might be controlled by throttling at the valves. 
The effect of unequal heads on the rate of filtration, where some of the 
.liters might be freshly cleaned and others badly clogged, can readily 


Fig. 129.—Inlet, Albany Filters. 

(From Trans. Am. Soc. C. E., vol. xliii.) 







































SAND FILTRATION. 


d52 

be imagined. Independence of action, especially as respects maximum 
rate, is greatly to be desired and is now required on all German filters. 

The regulation of head requires, first, some form of measuring 
device, such as a weir or orifice, by which the rate of filtration can be 



Fig. 130.—Regulating-valve, Rock Island Filters. 

ascertained at any time by floats and indicators; and, second, the con¬ 
trolling of the head on this weir or orifice either by hand or automati¬ 
cally. Floats are also required to show the level on the filter and the 
head in the main drain, the difference of which is the working head on 
the filter. The apparatus for regulation is placed in one or more 
chambers with which the main drain of the filter connects. 

523. Hand Regulation is accomplished either by varying the eleva¬ 
tion of the weir or orifice itself, and so enabling the level of the water 
to be varied without changing the rate of flow, or by maintaining a 
constant head on the weir by varying the opening in a valve as the 
filter becomes clogged. 

The first plan is that followed at Hamburg, the regulating arrange- 

1 

ments for which are shown in Fig. 131. The head on the filter at any 
time is the difference in level between the water in the filter and that 
in the main drain and chamber connecting therewith; it is indicated by 
suitable floats. The head on the weir, or the rate of filtration, is also 
indicated by floats, and is kept constant by moving the weir from time 
































































REG ULA TION OF FIL TFRS. 


453 


to time as the filter becomes clogged. This arrangement is very 
similar to that recommended by Kirkwood for St. Louis. Instead of 
a weir like that shown in Fig. 131, a telescopic tube has been used ir 



Fig. 131.—Regulating-apparatus at Hamburg. 

some places, similar to the form shown in Fig. 134, but adjusted by 
hand. 

The apparatus used at Berlin is illustrated in Fig. 132. In this 
the weir is fixed and the height of water on the weir is maintained at 
any desired constant level by regulating 
the sluice-valve between the two cham¬ 
bers. A somewhat similar scheme is 
used at Albany and is illustrated in Fig. 

133. The measuring is done by means 
of an orifice in a wooden partition, a 
head of I foot on this orifice being 
necessary to pass the standard quantity 
of water. This head is varied by means 
of the gate-valve admitting water from Fig , 32 ._ Regulating . apparatus 
the under-drains. The actual head on AT Berlin. 

the filter is measured by the difference between the water-level in the 
filter and the pressure-head in the pipe just back of this valve. Small 
float-chambers are provided, connecting with the different points, and 
suitable floats indicate the loss of head and the rate of filtration. When 
the rate of filtration exceeds the demand, the level of the water in the 
clear-water well gradually rises above the orifice, thus decreasing the 
rate to correspond to the reduced demand. This arrangement was 
adopted on account of the small size of the clear-water reservoir which 


















































































454 


SAND FILTRATION. 


local conditions made necessary. Only so much capacity was provided 
as was necessary to give a reasonable time for the filters to respond to 
the variations in the demand. The advantage of this arrangement is 
a smaller loss of head in the system, a smaller clear-water reservoir. 



Fig. 133. —Regulating-chamber, Albany Filter-beds. 

(From Trans. Am. Soc. C. E., vol. xliii.) 

and a partial automatic regulation of the filters to furnish the desired 
quantity of water. 

524. Automatic Regulation. —Automatic regulators for delivering 
water at a constant rate are in use in a number of places. They 
usually consist of a weir in the form of a telescopic tube which is sup¬ 
ported by means of a float in the chamber connecting with the under¬ 
drain. By adjusting the float, the edge of the weir can be maintained 
at any desired distance below the water-surface. A weir of this gen¬ 
eral type is illustrated in Fig. 1 34.* In this particular form, however, 
the water passes through vertical slotted holes near the top of the tube, 
and these openings may be varied in amount by partially covering 
them with a slotted collar placed within the tube. A form of balanced 
pressure-valve devised by Burton t and used for automatic regulation is 
illustrated in Fig. 135. The quantity of water passing the valve is 
maintained constant by keeping the difference of pressure on the two 
sides of an orifice in the plate e a constant quantity. This is done 
automatically by the balanced valve c , controlled by the piston d y 

* Report of Commission on Philadelphia Water-supply, 1899. 
f Proc. Inst. C. E., cxti. p 321. 


































































































































































GENERAL ARRANGEMENT OF PIPING. 4; 5 

N 

which is open to water-pressure both from the outside well and from 
the valve-chamber. 

525. Other Pipes and Valves.—Besides the inlet- and outlet-pipes, 
a drain-pipe must be provided through which the water may be drawn 
off. 1 his is usually connected with the chamber into which the main 
drain opens, as shown in bigs. 133 and 134. An overflow-pipe is also 
necessary to provide against any failure on the part of the inlet-regu¬ 
lator. This connects with the drain-pipe. (See also Fig. 128.) 

After a filter has been drained and cleaned it is desirable to fill 
with filtered water from below to a short distance above the sand. If 
the water in the pure-water basin is at a level higher than the surface 



Fig. 134. —Automatic Regulator. 



Fig. 135. —Automatic Regulating- 
valve. (Burton). 


of the sand, water can be admitted from it to the under-drains by 
means of a by-pass around the regulating-apparatus or through the 
partition-wall. If the pure-water basin is too low for this, water may 
be piped from an adjoining filter which is in operation. 

Arrangements should be made for wasting the filtered water in case 
it should be necessary, also for drawing off the water from above a filter 
down close to the sand layer in order to save time in emptying; and 
facilities should be provided for sampling water from various points in 
the system. By-passes should be provided to enable either settling- 
basin or filters to be cut out if necessity arises. For furnishing water 
for sand-washing and various purposes, connection must be made with 
high-pressure mains. 

526. General Arrangement of Piping. —The location of main supply- 
pipe, efifluent-pipe, and drain varies according to local conditions. 
At Albany (*Fig. 120) the supply-pipes and inlet-chambers are placed 
along one end of the beds, while effluent- and drain-pipes, with regu- 











































































456 


SAND FILTRATION. 


lating-chambers, are placed along the other end. At Hamburg a 
similar arrangement is adopted. At other places, as at Berlin, all 
pipes and chambers are placed along one side of the group of filters. 
This is a more compact arrangement, but makes a somewhat com¬ 
plicated network of pipes. Covered valve-chambers or gate-houses 
should be provided with open filters as well as with closed. 

527. Pure-water Reservoir.— Where practicable a pure-water reser¬ 
voir should be provided of sufficient capacity to prevent the necessity 
of frequent variations in the rate of filtration. If this is not done, it is 
at least necessary to furnish a capacious pump-well to prevent the fluc¬ 
tuations of the pumps from being directly felt by the filters. To enable 
the filters to be independently regulated the highest level in the pure- 
water reservoir should always be lower than the level of the water in 
the regulating-chambers of the filter. This may not always be practi¬ 
cable, as at Albany. From the data of Chapter II, Art. 31, it will be 
found that to equalize the supply for an ordinary day requires usually 
from two to three hours’ average consumption, and if the pure-water 
reservoir is given this capacity, plus a moderate fire reserve, it will be 
necessary to vary the rate of the filters but slightly from day to day. 

528. Cleaning Filters.—When a filter has become clogged and has 
reached its highest allowable loss of head, it is drained and then 
cleaned by removing by means of broad thin shovels a layer of clogged 
sand from \ to 1 inch in thickness. The surface is then smoothed with 
a rake. The sand is removed from the filter by means of wheelbarrows 
or small cranes, and deposited at a convenient point where it is cleaned 
after a considerable quantity has accumulated,—or is wasted in case it 
is cheaper to use new sand than to clean the old. After scraping, the 
filter is filled, preferably from below, with filtered water until covered 
2 or 3 inches deep; then raw water is run on to the usual depth, and 
the filter again started into action. At intervals of a year or so, and 
before the layer of sand has been reduced below a desirable minimum 
thickness, the bed is restored to its original depth by the addition of 
clean sand. The minimum thickness allowable by the German rule is 
12 inches, but a considerably greater thickness is to be preferred for the 
reasons already given in Art. 514. At the last cleaning before refill¬ 
ing, a thicker layer than usual should be removed, and the remaining 
sand to a depth of several inches dug over and loosened. This pro¬ 
cedure is to avoid the effect of stratification and to aerate the filter to 
some extent. At some works it is the practice to occasionally remove 
all the remaining sand and even the gravel. After cleaning and 
filling, the filter should be started slowly and gradually. At some 


PERIOD OF SERVICE. 


4S7 


works it has been found beneficial to allow the raw water to stand upon 
the filter for several hours before operation begins, in order that some 
sediment may collect on the surface and so hasten the establishment 
of the surface sediment layer. 

529. Cleaning Open Filters in Winter .—To accomplish this properly 
is the chief difficulty in operating open filters. If the ice is removed 
and the filter drained and cleaned in the usual way, there is much 
danger that the sand will be frozen and the operation of the filter 
greatly interfered with. It may also be very inconvenient to wait for 
a warm spell in which to do the work. To avoid removing all the ice, 
filters have been cleaned one-half at a time. The ice is removed from 
one-half of the bed, the bed drained, and that half cleaned. Water is 
then admitted, the remaining ice floated to the clean half of the bed, 
the bed drained, and the other half cleaned. At Hamburg, filters have 
been cleaned without draining by means of a special form of dredge 
suspended from a scow and pulled back and forth across the filter. 
The ice is broken up to make a passage for the boat, but it does not 
need to be removed. More recently a special device has been in use 
at Hamburg for cleaning under the ice.* It consists of a scraper and 
a large pouch to hold the sand. The whole is attached to a large 
float and is pulled back and forth under the ice by means of cables, it 
being thus necessary to cut away only a strip of ice along each side. 
When the scraper reaches one end, the pouch is emptied on the slope 
of the filter by turning it inside out, and the apparatus is then started 
back. 

530. Period of Service. —The period of service is the time that 
elapses between two scrapings of the filter. It may be measured in 
days or in an equivalent manner in terms of amount of water filtered. 
The period of service depends upon the character of the water, upon 
the fineness of the sand, and upon the maximum allowable loss of 
head. It is directly affected by the rate, a rapidly working filter be¬ 
coming clogged proportionally sooner. In practice it varies from a 
few days, if the conditions are specially bad, to 5 or 6 weeks where 
optimum conditions prevail. The amount of water filtered between 
cleanings ordinarily ranges from 40 to 80 million gallons per acre. 
For many waters the worst period is in the algal season. 

531. Effect of Scraping on Efficiency of Filtration.—In many cases 
there is a considerable decrease in the efficiency of a filter for some 
time after scraping, and in some works it is the practice to waste the 


* Jour. f. Gasbel. u. Wasservers ., 1897, XL. p. 4. 





45 « 


SAND FILTRATION. 


effluent for one or more days at this time. At other places it has been 
found sufficient to begin the operation very slowly after scraping. This 
method is followed in a number of the larger German filter-plants. In 
the Massachusetts experiments there was, in many cases, no deteriora¬ 
tion of the effluent after scraping; in others, such was not the case. 
As has already been noted (Art. 504) the effect of irregularities in 
operation, including that of scraping, was, in these experiments, 
greatest with thin filters and with coarse sand. The effect depended 
also upon the depth of sand removed and on the subsequent treatment. 
Filling a filter slowly from below was found to give much better results 
than filling from above. A good effect was also observed if the water 
was permitted to stand a few hours on the filter before starting the 
operation. If these precautions are followed, there is likely to be little 
need of wasting the effluent for any considerable time, but the necessity 
for this in any particular plant can be readily determined by experience. 
When the sand is renewed the necessity of wasting the effluent is much 
greater. 

532. Sand-washing.—Various methods have been employed for 
washing dirty sand, two of which deserve notice. The revolving drum 
washer, used largely in Germany, at Berlin and other places, consists 
of a large iron drum, slightly conical in form and open at both ends. 
The axis is horizontal. Sand is run in at the large end, and as the 
drum revolves it is gradually moved towards the smaller and higher 
end by means of interior screw-blades. Water enters at the other end 
and in flowing over the sand thoroughly cleans it. The amount of 
water required at Berlin is stated to be ten times the amount of sand 
washed, or about 2000 gallons per cubic yard of sand. 

The other form, known as the ejector sand-washer, has been in use 
in England for many years. It has also displaced the drum washer at 
Hamburg and is now employed in this country at several places. 
That used at Albany is shown in Fig. 136, and illustrates this type. 
The sand is passed through a number of ejectors, — in this case five. 
From the first hopper it is carried up the vertical pipe by a strong 
stream of water issuing from the nozzle below, thence flows into a 
second hopper where most of the dirty water escapes over the edge. 
It passes thence through the others in a similar way, finally being 
elevated and emptied into the clean sand-box. The quantity of water 
used with the washer is about 4000 gallons per cubic yard, and the 
capacity is 3 to 5 cubic yards per hour. 

533. Sedimentation in Connection with Filtration.—Many waters 
contain at certain times suspended matter to such an amount or of such 


SEDIMENT A TION IN CONNECTION WITH FILTRATION, 459 

a character as to render a preliminary treatment by sedimentation 
desirable or even necessary. Large quantities of clay or silt clog up a 
filter very quickly and seriously reduce its working capacity; and 


2lW'tIron Pipe 



Enlarged Section 
of Hopper. 




Longitudinal Section 


Hard Pine 


Fig. 136.— Ejector Sand-washer at Albany. 

(From Engineering News , vol. XL.) 

if the matter in suspension is very fine it passes into the filter and 
the effluent is likely to be turbid. River-waters are most subject to 
great turbidity, but even supplies derived from lakes may give trouble 
from this cause. A noteworthy example is at Ashland, Wis., where, 
during the “break-up” of the ice in the spring with strong wind 
action, the bay from which the water-supply is derived is rendered so 
turbid as to greatly impair the efficiency of the filtration process. 
Examinations made by Russell * during such a period showed only 20 
to 30 per cent bacterial efficiency. In some cases the period of service 
of the filters was reduced to four days; and under such conditions the 
effluent was quite cloudy. 


* Purification of Ashland Water-supply by Sand Filtration, 16th Rept. Wis. Bd. 
Health, 1895, p. 78. 









































































460 


SAND FILTRATION. 


The capacity of settling-basins or storage-reservoirs for preliminary 
treatment varies greatly in practice. For purposes of mere sedimenta¬ 
tion a capacity of more than one or two days’ storage will seldom be 
economical, but when the supply is taken from a variable stream it will 
often be advantageous to have a much larger capacity (Art. 463). In 
England the capacities adopted are relatively large,—usually several 
days’ supply (15 days in the case of one of the London works). In 
Germany, where reservoirs are provided, their capacity is usually quite 
small. 

To economize head, settling-basins are usually operated by the con¬ 
tinuous-flow method, and, if possible, are so located that the water 
flows by gravity from them upon the filters. Sometimes it is possible 
to place the settling-basin low enough to admit water to it from the 
stream by gravity, as in the case of tidal streams, but usually a low-lift 
pump is necessary. 

534. The Use of a Coagulant.—The experiments of Mr. George W. 
Fuller at Cincinnati on the Ohio River water have shown that with 
waters containing at times large quantities of very fine clay, the ordinary 
method of filtration preceded by plain subsidence is inadequate to give 
satisfactory results. The water experimented upon was exceedingly 
variable in character and often contained much sediment, the particles 
of which were less than 0.00001 inch in diameter. The experiments 
showed that for this water ordinary filtration would usually give a good 
effluent when the amount of suspended matter did not exceed 30 to 70 
parts per million, also that the water could at other times be properly 
prepared for filtration by coagulation and subsidence, and the resulting 
quality would then be perfectly satisfactory. With this double process 
the following average results were obtained: 


Bacteria in river water. . .10,200 

Bacteria in subsided water. 2,100 

Bacteria in effluent from Filter No. 16. 41 

Bacteria in effluent from Filter No. 17. 32 


The average amount of coagulant required for the process was 
estimated at 0.95 grain per gallon. 

The difficulty of filtering water containing much fine clay was also 
observed at Louisville and has been noted at Washington, D. C., and 
at other places; and for such waters as the Ohio and the Mississippi 
it is probable that a coagulant will have to be used at certain seasons 
of the year. However, until a much larger amount of data is accumu¬ 
lated than is now available, it will be the part of wisdom to move 
cautiously in the matter of definite recommendations as to best methods 







BACTERIAL CONTROL OF FILTER OPERATIONS. 461 

of treatment until experimental tests are made on the particular water 
in question. The experience at Louisville and Cincinnati has amply 
justified the expense involved in such preliminary tests. 

Where it is necessary to use a coagulant it should be employed in 
connection with the settling-basins, a matter which has already been 
discussed in Chapter XX. The construction and operation of the filters 
would be unaffected. 

535. Bacterial Control of Filter Operations. —The most accurate way 
in which to control the operation of filter-plants is to subject the water 
to a bacterial examination. This should be made at frequent intervals 
so as to note any possible changes in quality. The experience with 
European filter systems has shown that an impairment in quality has 
not infrequently been detected in time to prevent outbreaks of disease. 
In the larger filter-plants, a bacteriological laboratory should be 
installed, and daily tests of the effluent made. The filter-beds should 
be arranged so that the effluent from each can be tested separately, 
and provision made so that the filtered water can be rejected from 
any one filter if not up to standard.* In this way a scientifically con¬ 
trolled study can be made of all the filter operations and optimum 
conditions as to rate of filtration, cleaning, filling, etc., determined 
In Germany, compulsory examination of all sand filters is now in force, 
reports of the working of the same being sent to the Imperial Board 
of Health at stated intervals. 

The control of such operations is a matter of some importance. 
If the examinations are conducted under the direct supervision of the 
superintendent of works, it is possible to more satisfactorily study the 
problems that arise in connection with the operation of the filters; but 
at the same time, tests made by disinterested parties, such as Boards 
of Health, are received with more confidence by the public. The 
work, while requiring familiarity with bacteriological technique, is of 
such a character that it can be carried out under proper supervision by 
persons having but limited experience in bacteriological work. 

536. Rules for Bacterial Control .—The German Imperial Board of 
Health has formulated the following rules as applying to the question 
of sand filtration: 

1. Each filter shall be tested daily. This necessitates an arrange¬ 
ment to secure samples from drains at any time, a feature that is now 
regarded as essential for bacteriological work, but one which has fre¬ 
quently been neglected in past construction. 

* Koch traced the cholera outbreak In Altona in the winter of 1893 to the imper¬ 
fect operation of one filter. 





462 


SAND FIL TRA l lOD . 

2. Rate of filtration must not exceed 100 mm. per hour (2.57 
million gallons per acre per day). 

3. No filtered water should be admitted to the mains that contains 
more than 100 bacteria per c.c. To determine this count, he recom¬ 
mends gelatin incubated at 22° C. for two days. 

This quantitative limit is purely arbitrary, but good filter practice 
indicates that this is not beyond reach. Generally speaking, the 
average of properly constructed filters will probably fall below this, 
although, as has been noted previously, even in the best-manipulated 
filters there is considerable variation in germ content from day to day. 
In testing filters as to their efficiency, samples should be collected at 
periods when the effluent is likely to be the least favorable, as during 
frost periods, heavy rains, and periods of greatest consumption. 

537. Cost of Filters.—The cost of sand filters depends greatly upon 
local conditions as influencing cost of excavation, cost of sand, etc. 
Large beds and extensive works will cost less per unit area than 
smaller ones, other things being equal. At Berlin, covered filters of 
about 0.6 acre each have cost about $70,000 per acre. At Zurich, 
filters of acre each cost, for the masonry and filtering materials only, 
about $48,000 per acre for open and $72,000 for closed beds. 
Engineer Lindley estimates as a reasonable cost in Europe for care¬ 
fully designed filters about $68,000 per acre for covered and $45,000 
for open filters. 

At Ashland, Wis., three covered filters of ^ acre each cost 
$40,178, but the engineer estimated that under normal conditions the 
cost there would be about $35,000 for beds of acre each, which is 
equal to $70,000 per acre. At Poughkeepsie a single open bed of 
29,640 square feet cost $28,899, equal to $42,000 per acre. At 
Berwyn, Pa., three open beds of 7500 square feet each cost $18,536, 
equal to $36,000 per acre. The best figures at hand for the cost of 
filters on a large scale are those for the Albany plant. The cost for 
eight covered filters of an area of 0.7 acre each was $45,600 per acre, 
not including land and engineering; the latter item, figured pro rata 
from the total cost, would add about $2500 per acre. The covers were 
estimated to have added about $13,000 per acre to the cost. The cost 
■of covers is thus seen to be much less than indicated by European 
experience, due chiefly to the use of concrete and to a more economical 
design. To the cost of filters will have to be added the cost of dear- 
water reservoir, and usually sedimentation-basins, amounting to from 
$3000 to $10,000 per million gallons capacity according to the circum¬ 
stances. The total cost of the Albany plant, including the low-service 


COS T OF OPERATION. 


463 


pumping-station, but not including the conduit, was about $390,000, 
or $26,000 per million gallons capacity. 

538. Cost of Operation—The principal items in the cost of operation 
are the scraping of the filters, and the cleaning and renewal of the 
sand. The cost of scraping will ordinarily range from 80 cents to 
$1.20 per million gallons filtered, although removal of ice may greatly 
increase this. It is stated to have cost at London 86 cents per million 
gallons; at Liverpool, $1.14; at Hudson, N. Y., 88 cents; and at 
Poughkeepsie as high as $2.78, due to ice. At Lawrence, Mass., the 
cost of removal of ice in 1897 was about $2.00 per million gallons. 
The amount of sand removed may be taken at 1.5 to 2 cubic yards per 
million gallons filtered. The cost of washing is about 30 cents per 
cubic yard, making the cost per million gallons from 45 to 60 cents. 
Then the items of replacing the sand, repairs, and superintendence will 
bring the total operating expenses up to $2.50 to $3.50 per million 
gallons. At Poughkeepsie the average cost for twenty years has been 
$2.99 per million. 

The cost of operation at Albany, including superintendence, from 
July 26, 1899, to July 1, 1900, is given as follows:* 


Av. Cost per 1,000,000 Gals. 


Scraping. 

Wheeling out sand.. . 

Washing sand \ 

water. 


Refilling .. 

Cleaning sedimentation basin 
Incidentals. 


$0.25 
50 


54 

05 

39 

06 

20 


Total.$1.99 

Laboratory expenses.$0-34 


The total cost of filtration, including interest and depreciation, 
may, under ordinary circumstances, be estimated at from $7.00 to $9.00 
per million gallons filtered. 


INTERMITTENT FILTRATION. 

539. Theory of Action. —By intermittent filtration is meant filtration 
of water through sand in an intermittent instead of a continuous manner, 
thus permitting the filter-bed to be exposed to the influence of air dur¬ 
ing the periods of rest. This method of operation is more favorable to 
the nitrification of the organic matter in the case of a water deficient in 


* Eng. News , 1900, xi.iv. p. 88. 

















464 


SAND FILTRATION. 


oxygen than is the continuous method. The bacterial action of nitri¬ 
fication favors also the destruction of the water and other types of bac¬ 
teria, so that the result is an effluent that is often lower in bacteria than 
that of the continuous filter. The bacteria developing in the under¬ 
drains are also fewer. The yield of water is, however, less, because of 
the period of rest; so that the apparent superiority is not so evident 
when one takes into consideration the work performed. 

. 540. Construction and Operation.—The first intermittent filter-bed 
constructed in the United States was at Lawrence, Mass., built in this 
■way largely as the result of the Lawrence experiments. Besides the 
method of operation, certain other features are somewhat peculiar on 
account of the necessity for great economy. The filter is a single bed 
of 2^ acres and is constructed without a water-tight bottom. It is not 
of uniform depth or of uniform material. The drainage system is very 
much less extensive than in ordinary filters, considerable lateral move¬ 
ment through the sand thus being necessary. To cause a nearly 
uniform rate of filtration, a fine sand (.25 mm.) was placed over the 
drains and a coarser sand (.3 mm.) between the drains; and, further¬ 
more, the sand layer is made thicker in the vicinity of the drains than 
elsewhere, thus forming a series of ridges and hollows in the surface. 
Each day the water is drained off and the filter allowed to aerate; and 
at such times a portion of the bed can be cleaned. To enable the water 
to be quickly spread over the filter, concrete gutters are placed in each 
of the depressions in the surface of the sand. The cost of the filter 
(open) was only about $26,000 per acre. The filter was constructed 
on account of the prevalence of typhoid fever, and the results of its 
operation have amply justified the expenditure. Other filters operated 
on this plan are at Mt. Vernon, N. Y., and Grand Forks, N. D. 

The operation of intermittent beds is more troublesome and irregular 
than the continuous, and for ordinary waters intermittent operation does 
not appear to give better results; so that in most cases continuous 
filters with regulating apparatus would be preferable. In case of a 
very badly polluted water containing much organic matter, intermittent 
filtration would give better results, but it should be remembered that 
with so badly a polluted water as the Elbe at Hamburg and the Spree 
at Berlin the continuous system gives thorough satisfaction as judged 
by the decrease in the death-rates. 

541. Double Filtration.—This plan has been proposed for very bad 
waters, it being suggested that the first filtration be on the intermit¬ 
tent plan as in sewage filtration, while continuous filtration would be 
used for the second. No such a system has, however, been actually 


LI TER A TURK. 


465 


installed. But double filtration with both filters operating on the 
continuous plan is in actual use in two or three places in Europe. 
Considerable difficulty is met with in getting good work from the second 
filter, apparently on account of a lack of substances in the water which 
will form the gelatinous coating on the sand grains essential to efficient 
operation. 


LITERATURE. 

(See also p. 400)., 

ARTICLES OF A GENERAL CHARACTER. 

1. Kirkwood. Filtration of River-waters. New York, 1869. 

2. Frankland. Water Purification; its Biological and Chemical Basis. 

Proc. Inst. C. E., 1885-86, lxxxv. p. 197. 

3. Bertschinger. Experiments at Zurich on the Influence of Rate, Scraping, 

etc. Jour. f. Gas. u. Wasservers., 1889, 1891. 

4. Drown. Filtration of Natural Waters. Jour. Assn. Eng. Soc., 1890, 

ix. p. 356. 

5. Massachusetts Board of Health. Special Report, 1890, and Annual 

Reports since, contain results of the very valuable experiments of 
the Lawrence Experiment Station. 

6 . Frankel and Piefke. Leistungen der Sandfiltern. Zeit. f. Hyg., 1890, 

vm. p. 38. 

7. Piefke. Aphorismen ii. Wasseranlagen, Einrichtung u. Betrieb von 

Filteranlagen. Zeit. f. Hyg., 1890, vm. p. 331. 

8. Piefke. Neue Ermittelungen iiber Sandfiltration. Jour. f. Gas. u. 

Wasservers., 1891, xxxiv. p. 208. 

9. Sedgwick. The Purification of Drinking-water by Sand Filtration; Its 

Theory, Practice, and Results; with Special Reference to American 
Needs and European Experience. Jour. New Eng. W. W. Assn., 
1892, vii. p. 103. 

10. Frankland. The Micro-organisms in Water. London, 1894. 

11. Sand-washing Apparatus for Filter-beds. Engineering , 1892, liii. 

p. 621. 

12. Burton. Regulating the Rate of Filtration through Sand. Proc. Inst. 

C. E., 1892-93, cxii. p. 321. Describes a regulating-valve. 

13. Kiimmel. Versuche und Beobachtungen liber die Wirkung von Sand¬ 

filtern. Jour. f. Gas. u. Wasservers.^ 1893, xxxvi. p. 161. 

14. Mills. Purification of Sewage and Water by Filtration. Trans. Am. 

Soc. C. E., 1893, xxx. p. 350. 

15. Kiimmel. Some Questions concerning the Filtration of Water. Trans. 

Am. Soc. C. E., 1893, xxx. p. 330. 

16. Koch. Wasserfiltration und Cholera. Zeit. f. Hyg., xiv. p. 393. 

17. Piefke. Ueber die Betriebsfiihrung von Sandfiltern. Zeit. f. Hyg., 1894, 

xvi. p. 151. 

18. Fuller. Continuous and Intermittent Sand Filtration of Water. Am. 

Pub. Health Assn., 1894, p. 64; Eng. News , 1894, xxxn. p. 271. 

19. Reinsch. Die Bakteriologie im Dienste der Sandfiltration. Cent. f. 

Bakt., 1894, xvi. p. 881. Account of the operation of the Altona 
filters. 


4 66 


SAND FILTRATION. 


20. C. Frankel. Wasserfiltration und Rieselwirtschaft. Hyg. Rund., 1896, 

vi. No. 1. 

21. Fuertes. Some of the Factors which Determine the Efficiency of Filters 

for Water Purification. E?ig. Record , 1896, xxxiv. p. 160. 

Describes several regulating devices. 

22. Hazen. Mechanical Analysis of Filtering Materials. Eng. Record, 

1897, xxxv. p. 163. 

23. Magar. Reinigungsbetrieb der offener Sandfilter des Hamburger Filter- 

werkes in Frostzeiten. Jour. f. Gas. u. Wasservers., 1897, p. 4; 
Eng. Record , 1897, xxxv. p. 471. Describes device for cleaning 
filter-beds under the ice. 

24. Pannwitz. Die Filtration von Oberflachenwasser in den deutschen Was- 

serwerken wahrend der Jahre 1894—1896. Contains many full and 
valuable data. Arb. a. d. Kais. Gesundheitsamte, 1898, xiv. p. 153. 

25. Kemna. The Biology of Sand Filtration. Read before the Annual Con¬ 

vention of the British Association of Water-works Engineers. 
Abstract in Eng. News , 1899, xli. p. 419. A study of the organ¬ 
isms of the sediment-layer of filters. 

26. The Operation of Water-filters in Germany. Eng. Record , 1899, xl. 

p. 32. New regulations for operation. 

27. Gotze. Doppelte Sandfiltration fur Centrale Wasserversorgung. Arch.. 

f. Hyg., xxxv. p. 237. 

28. Gregory. Economical Dimensions of Rectangular Filter Beds. Eng. 

News, 1900, xliv. p. 252. 

29. Beer. Die Arbeiten der Commission deutscher und auslandischer Filtra- 

tions-Techniker und Erfahrungen liber Sandfiltration. A valuable 
review of filtration in Germany. Jour. f. Gas. u. Wasservers., 1900, 
xliii. p. 589. Abs. Eng. Record ' f 1900, xlii. p. 416. 


ARTICLES RELATING TO SPECIFIC WORKS. 

1. Halbertsma. Filteranlagen in den Niederlanden. Jour. f. Gas. u. Was¬ 

servers., 1892, xxxv, p. 43. 

2. Halbertsma. Ueber Filterregulirapparate und die Wasserleitung von 

Leeuwarden. Jour. f. Gas. u. Wasservers., 1892, xxxv. p. 686; 
Eng. News, 1893, xxix. p. 220. 

3. Preller. Water-supply, Power, and Electric Works of Zurich, Switzer¬ 

land. Proc. Inst. C. E., 1892-93, cxi. p. 257. 

4. Fowler. The Filter-beds at Poughkeepsie, N. Y. Eng. News, 1892, 

xxvii. p. 432. 

5. Mason. The Neckar River Water-filtration Plant at Stuttgart, Germany. 

Eng. News, 1893, xxx. p. 451. 

6. Mills. The Filter of the Water-supply of the City of LawTence and its 

Results. Report Mass. Board of Health, 1893, p. 543; Jour. New 
Eng. W. W. Assn., 1894, ix. p. 44. 

7. Sand Filtration at Hudson, N. Y. Eng. A T ews, 1894, xxxi. p. 487. 

8. Aeration and Continuous Sand Filtration at Ilion, N. Y. Eng. News y 

1894, xxxi. p. 466. 

9. Aeration and Intermittent Sand Filtration at Mount Vernon, N. Y* 

Eng. News , 1894, xxxn. p. 155. 

10 . Meyer. Das Wasserwerks Hamburgs. Hamburg, 1894. 


LI TER A TURE. 467 

11. Gill. The Filtration of the Miiggel Lake Water-supply, Berlin. Proc. 

Inst. C. E., 1894-95, cxix. p. 236. 

12. Sand Filter-beds at Grand Forks, N. Dak. Eng. News, 1895, xxxm. 

P- 34 i. 

13. Grahn. Wasserreinigung und Filtration fur die Wasserwerksanlage der 

Stadt Magdeburg. Jour. f. Gas. u. Wasservers., 1895, xxxvm. 
p. 85. 

14. Schroder. Die Betriebsandwaschen der Hamburger Filteranlagen. Zeit. 

d. Ver. deutsch. Ing., 1895, xxxix. p. 834. 

15. Halbertsma. Die Resultate der doppelten Filtration zu Schiedam. 

Jour. f. Gas. u. Wasservers., 1896, xxxix. p. 467. 

16. Hungerford. Sand Filter-beds for the Water-works of Lambertville, 

N. Y. Eng. News, 1896, xxxvi. p. 4. 

17. Gotze. Verbesserungen und Ersparnisse im Wasser-Filtrations-Betrieb. 

Jour. f. Gas. u. Wasservers., 1896, xxxix. p. 2. Relates to double 
filtration at Bremen. 

18. Wheeler. Masonry-covered Sand Filter-beds at Ashland, Wis. Jour. 

New Eng. W. W. Assn., 1897, xi. p. 301; Eng. News, 1897, 
xxxviii. p. 338. 

19. Fowler. Slow Sand Filtration at Poughkeepsie, N. Y. Jour. New Eng. 

W. W. Assn., 1898, xii. p. 209. 

20. The New Covered Filter-beds for the Water-works of Somersworth, N. H. 

Eng. News, 1898, xl. p. 358; Eng. Record, 1898, xxxvm, p. 271. 

21. Water Purification at Wilmington, Del. Eng. News, 1898, xl. p. 146. 

Specially designed plant for treatment with iron and rapid filtration. 

22. Fuertes. Water Filtration, Zurich, Switzerland. E?ig. Record, 1899, 

xxxix. p. 472. 

23. Ledoux. A Sand-fiiter Plant, Berwyn, Pa. Proc. Eng. Club Phila., 

1899, xvi. p. 108. 

24. Recent Experience with the Lawrence Filter. Eng. Record, 1899, xl. 

p. 597. Describes trouble with clogging by iron and crenothrix, 
and method of cleaning. 

25. Kiersted. Water-supply and Purification Works at Parkville and Bethany, 

Mo. Sedimentation and Filtration. Eng. News, 1899, xlii. p. 388. 

26. Ice Elevator at the Lawrence Filter-beds. Eng. Record, 1899, xl. 

p. 650. 

27. Hazen. The Albany Filtration Plant. Trans. Am. Soc. C. E., 1900, 

XLIII. p. 244. 

28. Slow Sand Filtration, Nyack, N. Y. Eng. Record, 1900, xli. p. 397. 

29. Operation of the Water-settling and Filtration Plant at Albany, N. Y. 

Eng. News, 1900, xliv. p. 88. Results for 1899-1900. 


CHAPTER XXII. 


MECHANICAL FILTRATION. 

542. General Description of the Mechanical Filter.—This type of 
filter, so called only because machinery is commonly used in raking 
and agitating the sand during cleaning, is also called the American 
filter or the rapid filter. It is a form of filter designed to accomplish 
results in the way of purification comparable with those obtained by the 
slow sand filter already discussed, but with a much smaller sand area. 
It is like the sand filter in that the filtering material consists of a bed 
of 2 to 4 feet of sand or crushed quartz, but in other respects the con¬ 
struction and operation are widely different. The chief points are: the 
very rapid rate of filtration (100 to 125 million gallons per acre per 
day), the use of a coagulant to aid in filtration, and the manner of 
washing the sand-bed. Methods of operation and mechanical details 
are, to a large extent, covered by patents, and the filters are manu 
factured and sold by various filter companies. 

Briefly, the filter consists of a wooden or steel tank in which the 
filtering material is placed and supported on a system of screens of 
various designs. In some forms the tanks are open and operated by 
gravity, and in others are closed and operated by pressure from the 
pipe system. When the filters become clogged through the accumu¬ 
lation of sediment on the surface, they are washed by forcing water in 
a reverse direction through the sand. During this process, the sand 
is, in most cases, agitated by means of mechanical agitators reaching 
deeply into the sand layer, or by means of compressed air. 

543. Types of Mechanical Filters.—Two well-known types of filters 
are illustrated in Figs. 137.and 138. In the first, the water enters the 

settling-chamber at the bottom, passes up through the central tube to 

• 

the top of the filter and thence downwards through the sand to the 
collecting-pipes located between filter and settling-tank. Where a co¬ 
agulant is used it is introduced before admission to the filter bed. The 
figure shows the agitators which are operated when the filter is washed. 
When not in use they are raised out of the sand. The wash-water 
passes off on all sides over the top of the inner tank. In the other 

468 



TYPES OF MECHANICAL FILTERS . 


4O9 


type the settling-tank is not connected with the filter. No agitators 
are used, but to loosen the sand air is passed through the bed from 
below. In both forms shown the filtration is by gravity. The Warren 



Fig. 137. —Jewell Gravity Filter. 


filter is another type commonly employed. It uses agitators like the 
Jewell, but the settling-tank is disconnected from the filter. 

544. Principles of Operation.—The action of mechanical filters is 
somewhat unlike that of sand filters, although the results are not greatly 
different. The effect of a coagulant in gathering the sediment into 
relatively large masses has been explained in Chapter XX. It aids 
filtration in this way and also forms a substitute for the organic coating 
on the sand grains and on the surface of the ordinary sand filter. It 
is the use of the coagulant which enables such high velocities to be 
employed. To avoid too frequent washing, it is common to employ 
heads as high as 10 to 12 feet, but with such high heads and velocities 
the sand becomes clogged to a considerable depth. The methods of 
washing, however, enable this sediment to be readily removed. The 
interval between washings, i.e., the “run,” is 24 hours or less, and 
the operation of washing requires about 15 to 20 minutts. The 



































































































































4/0 


MECHANICAL FILTRATION. 


amount of wash-water used is commonly from 2 to 5 per cent of the 
applied water, which fact must be considered in determining the gross 
capacity of the plant. Crushed quartz is often used for the filtering 


r% 



material, but ordinary sand would probably do as well if of very 
uniform grain so as not to be carried away in the washing process. 

The coagulant employed is usually sulfate of alumina, but common 
alum is sometimes used. The relative merits of these and some other 
coagulants have been discussed in Chapter XX. Quite recently, at 
Quincy, Ill., an iron coagulant, made by dissolving iron by the burning 
of sulfur, has been employed. It is reported to be much cheaper than 
sulfate of alumina, which it has there replaced.* 


* Eng. Record , 1899, XXXVII. p. 594. 










EXPERIMENTS ON MECHANICAL FILTERS. 


471 


In the operation of these filters one of the chief difficulties encoun¬ 
tered has been to wash the sand uniformly and to leave it in uniform 
condition after washing. The rakes used in agitating the sand are of 
much value in this connection. In many of the first plants the regula¬ 
tion of the rate of filtration and the quantity of chemical applied was 
very poorly done, but in some of the latest designs very efficient 
devices have been introduced to accomplish these objects. Other 
points of importance are mentioned further on. 

545. Extent of the Use of Mechanical Filters.—Mechanical filters are 
now in use in perhaps one hundred and fifty places in the United States 
(see Art. 485). In a large proportion of these places they have been 
adopted with particular reference to the removal of turbidity or color, 
and in others for the removal of precipitated iron in the purification of 
certain ground-waters (see Art. 563); but in some of the more recent 
plants the elimination of bacteria has been the chief object. Under 
these circumstances it is to be expected that until recently there should 
have been little reliable data concerning the bacterial efficiency of 
these filters. If their efficiency can be shown to equal that of the slow 
sand filters, the question as to the most feasible filter system to install 
in any particular case is primarily one of economy of first cost and cost 
of operation. 

546. Experiments on Mechanical Filters and Results of Operation.—. 

Important experiments on mechanical filters have been carried out at 
Providence in 1893—4 by Mr. E. B. Weston; at Louisville and Cin¬ 
cinnati by Mr. George W. Fuller in 1895-6 and 1898 respectively; 
and at Pittsburg by Mr. Allen Hazen in 1897. Each of these series 
extended over a considerable length of time and was very carefully 
conducted. Several shorter series of analyses from plants in regular 
operation are available and give valuable information. 

The Providence experiments were conducted on a small experi¬ 
mental Morison filter. The results were of a rather varying character, 
but when the filter was considered to be under normal conditions the 
removal of bacteria was from 95 to 99.9 per cent, averaging about 98 J 
per cent. The number in the original water was usually from 3000 to 
10,000 per cubic centimeter. The rate of filtration was 128 million 
gallons per acre per day.* 

547. The Louisville Experiments, t—These experiments were under¬ 
taken to determine the efficiency of mechanical filters in the purification 
of the Ohio River water. Besides important results as to bacterial 

* Report of the Rhode Island State Board of Health, 1894. 
f Fuller. Water Purification at Louisville. New York, 1898 






472 


MECHA NIC A L FIL TRA TJ ON. 


efficiency, much of value was derived in regard to features of construc¬ 
tion and operation. Unusual difficulties attended the operation at this 
place on account of the great amount of sediment carried at times, its 
greatly varying character, and the fact that the water did not undergo 
a preliminary subsidence. 

With regard to the qualitative results, the turbidity was practically 
all removed and also a part of the dissolved organic matter. The 
bacterial efficiency was irregular, but when the filters were operated 
normally the efficiency averaged from 97J to 98J per cent in the 
various systems experimented with. The presence of undecomposed 
alum in the effluent was noted for a short time,* due to carelessness, 
but such an occurrence was deemed entirely unnecessary, with proper 
superintendence. 

The greatest fault of all filters was the lack of adequate settling- 
tanks, the capacity of those used permitting only from 20 to 60 minutes 
of subsidence as a maximum. This necessitated the use of as high as 
8 grains p‘er gallon of coagulant. Poor facilities were also provided for 
the cleaning and inspection of the settling-chambers. The efficiency 
was greatly affected by the varying character of the water and by 
irregularities in the application of the coagulant, it being found very 
essential that the coagulation be thorough. In no case did the filters 
give results satisfactory from the standpoint of economy and efficiency, 
chiefly because of the lack of a previous settling of the water; and sucn 
subsidence for a day or more is regarded as imperative in the treatment 
of this water. With such subsidence, however, it was estimated that 
the average amount of coagulant (sulfate of alumina) would be about 
1.7 5 grains per gallon, and with proper attention to the operation it 
was considered that the result would be thoroughly satisfactory under 
all ordinary conditions. 

Mr. Fuller considered it desirable to employ a layer of sand at U<±st 
30 inches in thickness and of an effective size of 0.35 mm., in order to 
increase somewhat the frictional resistance over that offered by the 
sand used, which was from 0.43 to 0.51 mm. in diameter. The per¬ 
missible rate was considered to be 100 million gallons per acre, or 
over, and the maximum loss of head about 10 feet. In washing, i'~ 
was observed that agitators were of much help, and if the washing was 
thoroughly done no deterioration of the effluent was noticeable on the 
renewal of operations. 

548 . The C incinnati Ex pci imciits . f — These experiments were 
undertaken primarily to determine the applicability of the ordinary 


* This can be readily detected by using the logwood and acetic-acid test, 
f Fuller. Report on Water Purification. Cincinnati, 1899. 




EXPERIMENTS ON MECHANICAL FILTRATION. 4/j 

sand filters, and this phase of the subject has already been discussed 
on page 460. At the same time a mechanical filter of the Jewell type 
was experimented with, using water which had undergone plain sub° 
sidence. The character of the water is similar to that at Louisville. 
The general result as to efficiency was the removal of an average of 
98^ per cent of the bacteria, the original number averaging about 
27,000. Excluding results obtained at the time when certain changes 
were being made in the sand, the efficiency was 99.4 per cent, with an 
average application of 1.25 grains of sulfate of alumina per gallon. 
Mr. Fuller considered that with about one-third of a grain in addition, 
“ the bacterial results would be as good as is practicable to obtain by 
any method now known; that is to say, the bacteria in the effluent 
would average less than 100 per cubic centimeter, and the average 
annual removal of the river-water bacteria from present evidence would 
amount to fully 99J per cent. ” This is a considerably higher efficiency 
than obtained at Louisville, but in the latter case no preliminary sub¬ 
sidence was allowed. 

Regarding the relative advantages of mechanical filters, and sand 
filters with the use of a coagulant, Mr. Fuller considers that the former 
“ would be the less difficult to operate, would be somewhat cheaper, 
and would give substantially the same satisfactory quality of filtered 
water; and could be much more readily and cheaply enlarged for future 
requirement. 

Other points of value deduced from these experiments were, that 
sulfate of alumina was the best coagulant, that the maximum loss of 
head should be 10 or 12 feet, that the rate could be 125 million gallons 
or perhaps more, and that provision for at least 6 hours’ flow should 
be made for coagulation and subsidence immediately previous to filtra¬ 
tion. The amount of wash-water used was about 5 per cent, the aver¬ 
age time of washing 30 minutes, and the average frequency 15 hours. 

549. The Pittsburg Experiments .*—These experiments were made 
on two experimental sand filters, one Jewell and one Warren mechanical 
filter, and a set of artificial-stone tiles of the Fischer system (see page 
479). The average bacterial results for seven months were as follows: 

Bacteria Efficiency 
per c.c. per cent. 


River water. n .337 

Effluent from Warren filter. 20if 98.2 

Effluent from Jewell filter. 293! 97.2 

Settling-basin for sand-filters. 9. 22 4 

Effluent from sand-filter No. 1 . 106 99.1 

“ “ “ “ “ 2. 148 98.7 


* Report of the Filtration Commission. Pittsburg, 1899. 

\ Excluding inferior results obtained during special experiments. 












474 


ME CHA NIC A L FIL TRA TION. 


Sand filter No. 2 was operated for four months with unsettled water, 
otherwise the water for the sand filters was given from 12 to 24 hours’ 
subsidence. The mechanical filters were operated without preliminary 
subsidence. The efficiencies obtained throughout the tests were in 
general very uniform, but a lessened efficiency frequently followed, for 
a short time, the washing of the mechanical filters. The amount of 
coagulant was found to be of vital importance, and up to 1 grain per 
gallon the efficiency increased rapidly with the coagulant. With no 
coagulant it was only 50 or 60 per cent. 

550. Other Experiments and Tests .—The city of Lorain, Ohio, is 
supplied by water from Lake Erie which is considerably polluted by 
sewage, but still has relatively low numbers of bacteria and little tur¬ 
bidity. A Jewell mechanical-filter plant of 3 million gallons capacity 
was installed there, and previous to its approval by the Ohio State 
Board of Health was subjected to a five weeks’ test of efficiency under 
Mr. Hazen, with the following average results: 

• J 

RESULTS OF TESTS AT LORAIN. 



Alum used in 
Grains per Gal. 

Bacteria in 
Lake Water. 

Bacteria in 
Effluent. 

Rate of Filtration. 
Millions of Gals, 
per Acre per Day. 

1 st week. 

2.47 

I44I 

16 

67 

2 d “ . 

2.87 

385 

6 

69 

3 d “ . 

2.42 

367 

9 

70 

4th “ . 

1-35 

154 

14 

80 

5th “ . 

0.97 

189 

26 

72 


About one-half of the albuminoid ammonia was removed, and all 
color, turbidity, sediment, and odor. The plant was approved subject 
to the conditions of a maximum rate of 100 million gallons per acre and 
the use of 2.5 grains of alum per gallon. 

The sand used in the filter was 0.4 mm. in effective size and had a 
uniformity coefficient of 1.7. The wash-water was 5.1 per cent of the 
water pumped. The cost of alum was 1.8 cents per pound. # 

A three months’ test of a Jewell filter at East Providence, R. I., 
conducted by Mr. E. B. Weston, gave the average results shown on 
the opposite page. One grain of sulfate per gallon was used.f 

The city of Washington is supplied with a water which is turbid for 
a large portion of the year, in spite of the fact that it passes through 
two large reservoirs. The effect of storage is in fact greater upon the 
bacteria than upon the clay. Experiments have recently been made 

* Eng. News , 1897, xxxvnr. p. 278. Report of Ohio State Board of Health, 1897, 

p. 154- 

\ Trans. Am. Soc. C. E., T900, xliii. p. 69. 




















EXPERIMENTS ON MECHANICAL FILTRATION . 475 

with a slow sand filter, and a mechanical filter using a coagulant. 
The results were, in general, better from the mechanical filter than 
from the sand filter, although neither gave at all times a clear effluent. 
The mechanical filter was recommended by Col. A. M. Miller, 


RESULTS OF TESTS AT EAST PROVIDENCE. 



Raw Water. 

Filtered Water. 

Per cent 
Reduction. 

Bacteria per c.c. 

570 

4-5 

99.2 

Total solids. 

45-6 

42.83 

6 

Hardness. 

18.1 

21.7 

20* 

Ferric oxide. 

0.83 

O.32 

6l 

Nitrogen as free ammonia. 

0.04 

O.03 

29 

“ “ albuminoid ammonia. 

0.29 

O. II 

63 

“ “ nitrates. 

0.67 

0-57 

15 

Color. 

0.58 

O. IO 

83 


engineer-in-charge, but it was believed by Mr. R. S. Weston, who 
reported on the chemical and biological work, that a sand filter with 
the aid of a coagulant would also give satisfactory results. This system 
was, however, not experimented upon.f 

A mechanical filter lately installed at Marinette, Wis., has recently 
been tested by one of us with the following results: 


RESULTS OF TESTS AT MARINETTE. 


Date, 1900 . 

Amount of 
Coagulant 
Used. 

Grs. per Gal. 

No. of Bacteria per c.c. in 

Determination of Color. 
Platinum Standard. 

Raw Water. 

Filtered Water. 

Raw Water. 

Filtered Water. 

T T . 

none 

226 

120 



“ 1 -j . 

< 4 

325 

202 

127 

no 



‘ * in . 

£ 

1 



LK i . 

44 21 . 

540 

244 

513 

435 

39 ° 

442 

225 

159 

1050 

1075 

ii 55 

386 

745 

640 

200 

1 . 2 

I . 2 

‘ * on . 

3 

4 

1 

III 

0.0 

0.0 

Oct. 2 . 

253 

270 

145 

89 

35 

25 

208 

I .O 

I .O 

“ 16 . 

if 

0 7 

0.7 

“ TQ . 

0.9 

0.8 

A v. 

Nr>V 12 . 

1 

0.9 

0. 8 

“ ? I,. 

if 

14 

O. 15 

0.15 

0.0 

* 4 22 . 

0.0 

“ oo . 

4 

if 

if 

if 

if 

if 

0.7 

0.6 

. 

4 4 24 . 

136 

64 

61 

0.7 

0.6 

. . 

44 20. 

0.0 

0.0 

.. 

44 'in, .. 

0.15 

0.0 

. 

per 1.. . 

117 

152 

0.15 

0.0 

“ c . 


0.15 

0.0 




Average No. p 

pf r.f . 

503 

130 







The raw water was taken from Green Bay, an arm of Lake Michigan, 
but the normal condition was disturbed from time to time through the 


* Increase. 


f Abstract of Report in En°. News, igoo, xliii. p. 315. 



































































476 


ME CHA NIC A L FIL TEA T10N. 


influx of river water, as is readily determined by the rise in color. 
Owing to the low bacterial content of the raw (lake) water, the per¬ 
centage removed is not as high as usual, although the effluent often 
contained less than ioo bacteria per c.c. With the quantity of coagu¬ 
lant (sulfate of alumina) employed, the color removal was not marked, 
only about o. i-o. 15 being removed in any case. 

551. Efficiency as Determined by Typhoid Statistics.—Although 
mechanical filters have been in use in American cities for a number of 
years, the results of their efficiency as determined by the typhoid statis¬ 
tics have not been widely collected. In general the data that have 
been rendered available do not show as good results as has been accom¬ 
plished by the introduction of sand filters, either in this country or in 
Europe; but in most instances the period reported on is not of suffi¬ 
cient duration to make the reports comparable with European figures. 

Hill* reports the typhoid rates per 100,000 population for 1896 in 
five American cities supplied with mechanical filters as follows: 


Davenport, la.20 

Atlanta, Ga. 60 

Chattanooga, Tenn.30 

Quincy, Ill.26 

Knoxville, Tenn.44 


Kober + has recently extended this series by the additions given in 
Table No. 72. 


TABLE NO. 72 . 

AVERAGE ANNUAL TYPHOID MORTALITY IN AMERICAN CITIES USING MECHANICAL 

FILTRATION. 



Average Annual 
Typhoid Mortality. 

Per cent 
Reduced. 

No. Years 
reported 
before and 
since 

Filtration. 

Establish¬ 
ment of 
Filter. 

Before 

Filtration. 

After 

Filtration. 

Macon, Ga. 

IO.5 

7 

33 

4 

1893 

Atlanta. Ga. 

6 l 

46 

25 

3 

I88l 

Oakland, Cal. 

19 

17 

II 

5 

1892 

Reading, Mass. 

4 

1 

75 

1 

1896 

Terre Haute, Ind. 

21.6 

15 

3 i 

5 

1890 

Elmira, N. Y. 

10 

11 

— 10 

1 

1898 

Newcastle. Pa. 

13 

28 

-II 5 

1 

1897 

Lexington, Ky. 

18 

64.2 

— 256 

4 

1895 


Even eliminating the results noted in the last three cities, the 
average reduction is only about 25 per cent; but not much reliance can 


* Public Water-supplies, p. 268. 

f Kober. Public Health Reports, U. S. Marine-Hosp. Service, June 22, 1900. 
































SUMMARY. 


477 


be placed on figures of this sort unless all conditions are known and 
taken into consideration, and the period of observation covers a con¬ 
siderable number of years. 

552. Cost.—The cost of a mechanical-filter plant appears to range 
from $7000 to $10,000 per million gallons capacity for filters and 
fittings. To this it is necessary to add the cost of housing, and in 
some cases that of settling-basins. The cost of operation is largely 
dependent upon the amount of chemical used. The cost of sulfate of 
alumina is usually from 1} to 2 cents per pound, which is equivalent 
to from $2.10 to $2.80 per million gallons for each grain per gallon 
used. Compared to the cost of sand filters the first cost will usually 
be less, but if much coagulant is used the cost of operation will be 
higher. The depreciation of the plant will also be higher. Which 
system would be the most economical would depend upon the character 
of the water treated and other local conditions. Mr. Fuller estimates 
for Cincinnati the total expense, including interest and depreciation, for 
the system of sand filters with coagulant, at $10.35 P er million gallons, 
and for mechanical filters $9.96. For Pittsburg, Mr. Hazen estimates 
the cost of the two systems at $10.53 an d $10.78 respectively. This 
includes considerable expense for pumping-stations, etc. Col. Miller 
estimated for Washington, D. C., a total cost for the slow sand filters 
of $8.50 per million gallons, and for mechanical filters $8.76. At 
Philadelphia the cost of operation alone is estimated at $4.80 for 
Schuylkill water and $4.00 for Delaware water, compared to $3.60 
and $3.00 for sand filters. 

553. Summary.—The experiments here described, and the results 
of operation elsewhere, indicate that when mechanical filters are 
properly operated, turbidity can be practically all removed, a large 
percentage of color, and a considerable portion of dissolved organic 
matter. . With the quantities of coagulant ordinarily used, they are 
probably slightly less efficient than sand filters in the removal of 
bacteria. In some places satisfactory clarification is obtained without 
a coagulant, but for good bacterial results a coagulant is necessary. 

To obtain uniformly good results with economy requires very care¬ 
ful operation. The coagulant must be closely regulated to correspond 
with the quality of the water;—in the case of waters low in alkalinity 
this is particularly necessary. The efficiency depends so entirely upon 
the control of these matters that the proper operation of a mechanical 
plant involves greater care on the part of the attendants than that of a 
sand filter. It is fully as important in this case also that the whole 
plant should be under the control of bacteriological tests, regularly and 


473 


MECHANICAL FILTRATION. 


frequently made. Many points of operation, such as period between 
washings, wasting of water, thickness of sand layer, and best kind of 
sand, can be learned only after experience in the light of such analyses. 

Considering the economic advantages of mechanical filters it may 
be said that they are especially adapted to those cases where the cost 
of land is high, where the water is so turbid as to require large settling- 
reservoirs with a sand-filter plant, and in small plants where the unit 
for sand filters would be very small. They are also well adapted for 
the rapid removal of iron from ground-waters or of the precipitate in 
softening plants (see Chapter XXIII). On the other hand, if the total 
annual expense of sand filters and mechanical filters is equal, the 
evidence points to the desirability of adopting sand filters, especially for 
sewage-laden waters, but the difference in efficiency is not great enough 
to warrant any considerable additional expense. With very turbid 
waters both systems are likely to prove unsatisfactory unless supple¬ 
mented by adequate settling-basins. 

LITERATURE. 

(See also references on page 400.) 

1. Weston. Rhode Island State Board of Elealth Report, 1894. Experi¬ 

ments at Providence. 

2. Warren Mechanical Filter. Eng. News, 1894, xxxi. p. 6. Describes a 

number of plants. 

3. Various Systems of Filtration at Denver, Colo. Eng. News, 1894, xxi. 

p. 83. 

4. The Jewell Mechanical Water-filter Plant at Wilkes-Barre, Pa. Eng. 

News, 1896, xxxv. p. 330. 

5. The Jewell Mechanical Water Filter in Nineteen Cities. Eng. News, 

1896, xxv. p. 354. 

6. Hazen. Report on the Mechanical Filtration of the Public Water-supply 

of Lorain, O. Ohio State Board of Health Report, 1897, p. 154. 

Abstract, Eng. A^ews, 1897, xxxvm. p. 278. 

7. Bacterial Test of a Mechanical Filter at Louisiana, Mo. Eng. News , 

1899, xlii. p. 318. 

8. Water Purification at Vincennes, Ind. Eng. News, 1900, xliii. p. 291. 

9. Water Purification at Norfolk, Va. Eng. News, 1900, xliii. p. 346. 

10. Weston. Test of a Mechanical Filter (East Providence, R. I.). Trans. 

Am. Soc. C. E., 1900, xliii. p. 69. 


CHAPTER XXIII. 


MISCELLANEOUS PURIFICATION PROCESSES. 

554. The Fischer Tile Filter.—This form of filter, invented by 
Director Fischer of the water-works of Worms, Germany, and used at 
that place, consists of a series of hollow cells composed of a mixture 
of sand and glass fused together. The cells are about 3 feet square 
and 8 inches thick, with a hollow space of about 1 inch. They are set 
up on edge in a reservoir containing the water to be filtered, and con¬ 
nected together in groups so that the water filters through into the 
interior space and thence passes out through suitable pipes. The 
filters are cleaned by reversing the flow, and by washing with a hose- 
stream. They can also be sterilized by steam. The rate of filtra¬ 
tion practiced at Worms is about 3 million gallons per acre per day, 
but the actual space occupied by the filters is only about one-fourth 
that of an ordinary filter. The results obtained compare very favor¬ 
ably with those from sand filters. The system is in use in several 
places in Europe. Several cells were experimented upon at Pitts¬ 
burg,* but they were not found very well suited for so turbid a water, 
the preliminary treatment there required accomplishing nearly all the 
purification. 

555. Aeration.—Attempts have often been made to purify water of 
organic matter by aeration. The presence of oxygen is certainly 
necessary for the action of the nitrifying organism, and experiments of 
the Massachusetts Board of Health show that artificial aeration greatly 
increases the rate of purification in the case of sewage filtration. But 
to add large quantities of oxygen to water that already contains oxygen 
appears, from experiments by Drown and from analyses of aerated 
Water in various places, to have little or no effect on the organic matter. 
Experiments on aeration were made by Drown f in several ways: 
(1) by exposing water in bottles to the air of a room; (2) by drawing a 


* Report of Filtration Commission, 1899, p. 202. 
f Mass. Board of Health, 1891, p. 385. 





480 


MISCELLANEOUS PURIFICATION PROCESSES. 


current of air through the water; (3) by shaking water in a bottle; and 
(4) by exposing water to air under a pressure of 60 to 75 pounds per 
square inch. . The results of some of the experiments are given in 
Table No. 73. The variations shown in the amount of albuminoid 

TABLE NO. 73 . 

RESULTS OF EXPERIMENTS ON AERATION OF COCHITUATE WATER. 


(Parts per 100,000.) 


• 

Free 

Ammonia 

Albumi¬ 

noid 

Ammonia. 

Nitrogen 

as 

Nitrites. 

Nitrogen 

as 

Nitrates. 

First experiment: 

Original sample.. 

.0014 

.0182 

.0002 

.0275 

After standing in open bottle for 48 hours. 

.0008 

.0176 

.0005 

.0250 

After aerating by current of air for 48 hours. . 

.0014 

.0170 

.0003 

.0250 

After standing in open bottle for 2i6|- hours... 

0036 

.0158 

.0002 

.0250 

After standing 49J hours and then aerating by 
a current of air for 167 hours. 

.0026 

•0156 

.0002 

.0250 

Fourth experiment: 

Original sample. 

.0018 

.0140 

.0002 

.0200 

After standing for 72 hours. 

.0016 

•0152 

.0002 

.0300 

After aerating “ “ “ . 

.0024 

.0142 

.0002 

.0200 

After being under pressure of 75 lbs. for 72 hrs. 

. 0036 

.0150 

.0002 

.0250 


ammonia are too small to be significant. Other experiments on very 
dilute sewage gave about the same results, with the exception that a 
part of the free ammonia was removed in the same way that any gas 
can be driven out by aeration. The general results of the experiments 
are confirmed by analyses made on river-waters at points above and 
below falls or rapids. 

Though aeration may effect little or no change in the organic 
matter present in a water, it does have a very important action in the 
case of waters from stagnant ponds and reservoirs in which putrefactive 
changes have taken place. Such waters will have offensive odors and 
tastes, due to the dissolved gases contained, and it is in the removal of 
these gases that the process of aeration can be successfully applied. 
It has been so used in a large number of cases. 

556. Aeration may be accomplished by forcing air into the mains, 
or by passing the water over cascades or weirs, or by spraying it from 
a fountain into a reservoir as is done in many places, or by still other 
methods. The largest plants designed especially for aeration are 
probably those of the Spring Valley Water-works of San Francisco. 
There are three separate plants, all of similar design. The one known 
as the College Hill plant has a capacity of 8 million gallons per day. 




















SOFTENING OF WATER. 


48! 


The water rises about 20 feet in an upright pipe, is then conducted 
through two long wooden flumes and distributed from these through 
holes in the sides, to a series of wooden platforms. These are about 
3 feet apart vertically and are made of i-inch plank 6 inches wide laid 
i inch apart. The result of the aeration appears in this case to be 
quite marked, according to the report of the Board of Health. The 
results are, for the three plants, as follows, in parts per 100,000:* 


Albuminoid ammonia : 

Before aeration. 

After aeration. 

Oxidizable organic matter: 

Before aeration. 

After aeration. 


I 

2 

3 

.00620 

.OO756 

.00756 

.00416 

.00252 

.00492 

.000 

4.24 

4 • 24 

.665 

2.94 

1.8o 


It is to be noted that the albuminoid ammonia is very low before 
treatment. 

Where waters are to be filtered that are deficient in oxygen some 
method of aeration should be employed. At Albany this aeration is 
accomplished by allowing the water to spray into the settling-reservoir 
through small holes in the vertical inlet-pipes (see pages 435, 437). 
Another use of aeration in the case of small reservoirs is the prevention 
of the growth of algae by the agitation produced by the process. In 
the removal of iron from ground-waters aeration plays an important 
part as more fully described in Art. 564. 

557. Softening of Water.—Water is rendered hard by the presence 
of lime and magnesia, chiefly in the form of carbonates and sulfates, 
but occasionally as chlorids and nitrates. The carbonates cause 
so-called temporary hardness (removable by boiling), while the sul¬ 
fates and other compounds cause permanent hardness. The various 
objections to a hard water have been fully pointed out in Chapter IX 
(page 143), but it may be well to repeat here the most important facts. 
In using a hard water for washing purposes approximately 2 ounces of 
soap are neutralized or wasted for each 100 gallons of water for each 
grain per gallon of calcium carbonate or its equivalent. In boiler use 
the carbonates of lime and magnesia are precipitated, forming a deposit 
which can usually be removed by blowing out, unless accompanied by 
scale-forming substances. Sulfate of lime precipitates at high tempera¬ 
tures and forms a very hard, objectionable scale, particularly if the 
water contains other suspended matter. The solubility of the sulfate 
is approximately given by the following table: 


* Eng. Record , 1896, xxxiv. p. 201; 1899. XL. p. 155. 







4$2 


MISCELLANEOUS PURIFICATION PROCESSES. 


Temp. 

Pressure, 

Grains per Gal 

Fahr. 

Lbs. above Atmospheric. 

CaS 0 4 . 

32 

• • • • 

Ill 

63 

• • • • 

120 

104 

• • • • 

125 

140 

• • • • 

121 

176 

• • • • 

114 

212 

O 

III 

284 

37-8 

45 

324-5 

80.8 

33 

356.5 

132.O 

16 

473 

513-5 

10 


Of the other substances the sulfate of magnesium is the most 
common. It is objectionable as tending to decompose at high tem¬ 
peratures, forming scale.. 

558. Chemistry of Water Softening. —The softening of water is 
accomplished by simple processes of chemical precipitation. To 
remove the carbonates, lime is used as the precipitant. The carbonates 
are held in solution chiefly by virtue of the carbonic acid dissolved in 
the water, and on adding lime the acid unites with it, forming carbonate 
of lime. In the case of hardness due to the carbonate of lime the 
reaction is 

CaC 0 3 + C 0 2 + €a(OH) 2 = 2 CaC 0 3 + H 2 0 . 

The resulting carbonate is now but slightly soluble and so precipitates 
out.* With the carbonate of magnesia, a similar reaction is presumed 
to first take place, thus: 

MgCO s + C 0 2 + Ca(OH) 2 = MgC 0 3 + CaC 0 3 + H 2 0 ; 

but as the carbonate of magnesia is quite soluble, a further quantity of 
lime is required to complete the process, thus: 

MgCO s + Ca(OH) 2 = Mg(OH) 2 + CaC 0 3 . 

The hydrate precipitates out. 

To remove the sulfates, sodium carbonate (Na.,C 0 3 ) is used. Lime 
must also be added in the case of magnesium sulfate. The reactions 
are: 

CaS 0 4 + Na 2 C 0 3 = CaC 0 3 + Na 2 S 0 4 , 

and 

MgSU 4 + Ca(OH) 2 + Na 2 C 0 3 = Mg(OH) 2 + CaC 0 3 + Na 2 S 0 4 . 

The sodium sulfate resulting from these reactions is very soluble and 
unobjectionable in the amount likely to be present. The chlorids and 
nitrates may be removed in the same way as the sulfates. 

* The lime may also be considered as being present as a bicarbonate, which 
changes to the insoluble carbonate when Ca(OH) 2 is added. 








SOFTENING OF WATER. 


433 


359 * The Lime Pi'ocess. —This process for the removal of temporary 
K^-xiness was invented in 1841 by Dr. Clark of England, and is com¬ 
monly known by his name. It has been used quite extensively in that 
ccuntry, where many towns are supplied with water drawn from the 
chalk deposits. Various methods of carrying out the details of the 
process, relating principally to the application of the lime and the 
removal of the precipitate, have been devised. These are known under 
various names, but the general principle is the same in all. The lime 
is usually added in the form of lime-water, although milk of lime was 
formerly used,. 

In the original Clark process the precipitate was removed by sub¬ 
sidence in large tanks. In the Porter-Clark process (one of the most 
commonly used processes) the water, after the application of the lime, 
rises slowly through an iron cylinder containing broad shelves on which 
the precipitate settles, and from which it is scraped at intervals by 
means of a series of paddles. The final cleaning takes place in 
settling-basins. Filter-presses similar to those employed in sewage- 
disposal works have been used for removing the precipitate. It would 
seem that the ordinary mechanical filter could be used here to very 
good advantage. 

Probably the largest softening plant yet constructed is that at 
Southampton, England, where the entire city supply is softened to the 
extent of reducing the hardness from 18 0 , Clark scale,* to about 6°. 
The capacity of the plant was, in 1892, 2,400.000 gallons per day. 
The lime is burnt in a kiln near at hand. The slaked lime is dissolved 
in the softened water in two large cylinders, the amount taken in solu¬ 
tion being about 75 grains per gallon. At this ratio it requires for this 
plant about one-tenth as much lime-water as the amount of water to be 
treated. After receiving the chemical, the water passes into a large 
cistern, where much of the precipitate settles; the finer particles are 
removed by a series of Atkin filters. These filters consist of perforated 
zinc disks covered with filter-cloths and arranged in pairs along a 
hollow shaft. They are immersed in the water to be filtered. The 
water passes through these disks to the space between them and thence 
through the hollow shaft to the outlet. The filters are cleaned every 
6 or 7 hours by spraying them from fixed perforated pipes, the disks 
and shaft being rotated at the same time. 

The cost of the plant is stated to be about $48,000, which is equiva¬ 
lent to $20,000 per million gallons capacity. The cost of operation is 
about $4.00 per million gallons.+ 

* i° = 1 grain of carbonate per Imperial gallon = 1 part in 70,000. 

f Proc. Inst. C. E.,1891-92, cvm. p. 285; Eng. News, April 16, 1892, p. 380. 







484 MISCELLANEOUS PURIFICATION PROCESSES. 

560. The Archbutt-Deeley Process. —In this process both lime and 
soda are used so as to remove both the temporary and the permanent 
hardness. The chief feature of the process is in the method of removal 
of the precipitate. The water to be treated is run into large tanks into 
which the chemical is introduced in the correct proportions and then 
diffused throughout the water by means of a steam-blower. The pre¬ 
cipitation is hastened by stirring up for about 10 minutes some of the 
previously accumulated sediment, an operation which is found to be 
very effective, the water becoming nearly clear in an hour or less. 
The little remaining matter in suspension is then redissolved and all 
traces of free alkali removed by introducing carbon dioxide from a 
small coke-stove. This recarbonating also makes the water more 
palatable. A plant of this sort at Swadlincote and Ashby, England, 
is stated to reduce the hardness of the water from about 23 0 to 8£°, 
and to remove a considerable amount of iron, at a cost of 1.6 cents 
per 1000 gallons. Lime only is there used. The capacity of the 
plant is 540,000 gallons per day. 

561. Softening of Water for Boiler Use .—In England, many plants 
for the softening of boiler feed-water are in operation, and recently 
several such plants have been inaugurated by railroad companies in this 
country. The operation of these plants has resulted in a great economy 
in locomotive maintenance. In purifying water for boiler use the pre¬ 
cipitate can be removed to a sufficient extent by the use of settling- 
tanks alone. The chemicals used are lime and usually soda ash, or 
crude sodium carbonate. The cost for such small plants is reported to 
be from 4 to 1 5 cents per 1000 gallons. 

Many scale preventives have been proposed for use in boilers, but 
probably the best in general use is sodium carbonate. This breaks up 
the sulfates as previously shown, and thus prevents the formation of a 
hard deposit; but the precipitation of the carbonates is increased by 
the process. The sodium sulfate remains in solution, but should not 
be allowed to concentrate too greatly or it will cause foaming. 

562. Bacterial Efficiency of the Softening Process. —Experiments 
by Frankland, and results of operation in practice, show a considerable 
degree of bacterial purification in the softening process,—in some cases 
quite as high as that of other processes. The precipitate is pulverulent 
instead of gelatinous in character, and experiments at Louisville 
showed the process to be in general quite inadequate for the removal 
of bacteria, unless lime be introduced in considerable excess (Art. 475). 

563. Removal of Iron from Waters .—Cause of Iron in Waters — 
Ground-waters may not infrequently contain iron in solution and so 




REMOVAL OF IRON FROM WATERS. 485 

have their taste and appearance impaired. Such waters are apt to act 
as astringents. Where iron is present in the proportion of 0.4-0.5 part 
per million, little or no trouble from taste or appearance is to be noted. 
An excess of iron, however, is not only disagreeable to the taste, but 
is objectionable for domestic use, especially in the laundry. 

The presence of iron in ground-waters is due to a series of chemical 
changes that are induced by the presence of organic matter. Most 
soils, as sands, gravel, etc., contain more or less iron, which is 
generally in the form of ferric oxid (Fe 2 0 3 ). As surface-waters perco¬ 
late into soil-layers containing organic matter, they are rapidly 
deprived, by the oxidation of the organic matter, of the free oxygen 
which they contain. When this supply of oxygen is used up, the 
organic matter attacks the insoluble ferric oxid, reducing it to ferrous 
oxid (FeO), which unites with the carbonic acid naturally present in the 
water, thus forming ferrous carbonate (FeC 0 3 ), which is soluble in 
waters of an acid reaction. Therefore, wherever the conditions in the 
soil favor these chemical changes, iron may appear in the water. In 
alluvial plains, river valleys, and similar locations, where organic 
matter is more or less abundant, waters of this class are often found. 
In a number of different cities along the Atlantic seaboard, as on Cape 
Cod, Long Island, and the Jersey shore, as well as in numerous loca¬ 
tions in the alluvial plains of Germany, Holland, and Denmark, trouble 
from such a source has been experienced. 

In such waters, the iron bacterium, Crenothrix, is very likely to 
grow. As this form develops in darkness, it is capable of multiplying 
in distributing-pipes, where it may sometimes accumulate to such an 
extent as to seriously interfere with the service. This organism lives 
on the soluble iron, utilizing it as a food, finally precipitating it as 
ferric oxid in its gelatinous sheath, and so causing the accumulation of 
flocculent masses. Upon the death and decay of these organisms, bad 
odors and unpleasant tastes may be produced. 

Waters containing these iron salts are clear when first drawn, but 
soon become cloudy on standing, due to the absorption of oxygen from 
air and the consequent conversion of the soluble ferrous salt into ferric 
hydroxid. This material in time settles out as a rusty precipitate. 
Sometimes where there is an abundance of organic matter in solution, 
as in waters from peaty sources, soluble compounds are formed with 
the organic matter that are not readily oxidized upon exposure to air. 

564. Treatment of Iron Waters .—It has been noted that in many 
cases where the iron is present as ferrous carbonate it will be removed 
by oxidation if exposed to the air. This reaction is utilized in the 


486 


MISCELLANEOUS PURIFICATION PROCESSES. 


practical treatment of such waters, and in most of the plants installed 
for the removal of iron from ground-waters aeration is employed 
to facilitate this oxidation. The precipitated iron (Fe 2 O s ) is generally 
removed from the water by filtration through sand. As a heavy 
flocculent deposit is produced that does not readily penetrate the filter, 
even where coarse sand is employed, rapid filtration is possible. 

To satisfactorily treat waters of this class, it is necessary to reduce 
the iron content to less than 0.5 part per million. The percentage of 
iron removed, therefore, is not of so much value as a determination of 
the content of the effluent. 

The extent of aeration required varies considerably, according to 
the character of the water, and the conditions necessary for successful 
treatment cannot in all cases be determined without experiment. In 
some cases simple exposure in open canals gives sufficient aeration, or 
the mere spraying in small jets, or other simple means may be success¬ 
ful. At Charlottenberg, and several other places in Germany, the 
water is passed through aerators made of coarse pieces of coke. At 
Beelitzhof the aerators are made of blocks of stone, and appear to work 
equally well. At Provincetown, Mass., Mr. H. W. Clark found that 
where simple aeration would not answer a coke-filter was successful, 
due, it was thought, to some chemical action of the coke. 

In some cases the difficulty of aeration is probably due to excess of 
free carbonic acid; in other cases, as at Reading, Mass., the iron is 
present as a sulfate. The addition of lime would solve the difficulty 
in the first case, while the use of lime and alum has proven successful 
in the case of the Reading water. At Provincetown Mr. Clark found 
that ferrous sulfate or ferric chloride would precipitate the iron. 

565. Application of Electricity to Water Purification.—Electricity is 
indirectly applicable to the purification of water in two ways: (1) the 
electrolytic production of a disinfectant and deodorizer; (2) the elec¬ 
trolytic production of a coagulant. In both of these cases it appears 
that the action of the substance produced is quite the same as when 
produced in other ways, and the question is primarily one of the eco¬ 
nomical manufacture of the substance in question. 

The principal method of producing the first-named class of com¬ 
pounds is by the electrolysis of salt-water or sea-water, producing 
thereby principally the hypochlorite of sodium, a powerful disinfectant. 
Electricity has also more recently been employed in the production of 
ozone. The action of substances of this character is discussed on page 
492. The process is one which has so far been chiefly limited to sewage 
treatment, but under certain conditions may prove of value in water 


THE ANDERSON REVOLVING PURIFIER . 487 

purification. It is used as the “Wolf process ” for the treatment of 
sewage of Brewsters, N. Y., a small village on the Croton watershed. 
Salt is added to water, electrolyzed, and then discharged into the 
sewer. 

The other general method has been applied to the production of 
hydrate of iron and hydrate of alumina, with results comparable with 
the use of those substances as already described. This subject was 
thoroughly investigated by Mr. Fuller at Louisville, with the conclu¬ 
sion “ that aluminum cannot be economically used in this way on 
account of its excessive cost. Aluminum in the sulfate is much 
cheaper per pound than the metallic aluminum. 

Regarding ferric hydrate, Fuller states that “ under practical Con¬ 
ditions this process (electrolytic) can be used to produce ferric hydrate, 
a good coagulant, up to the point where the atmospheric oxygen dis¬ 
solved in the water is not completely exhausted.” The cost of 
metallic iron is about 2 cents, and iron in the persulfate is 5 cents, thus 
leaving a considerable margin for the cost of the electrolytic process. 
Estimates of the cost for the treatment of 25,000,000 gallons of Ohio 
River water with the equivalent of 1 grain per gallon of sulfate of 


alumina were as follows: 

Electrolytic iron treatment.$63.24 

Persulfate of iron treatment. 44.62 

Sulfate of alumina treatment. 53-55 


A very considerable advantage of the electrolytic production of the 
coagulant is that it does not add any objectionable substance to the 
water, or increase its hardness. 

566. The Anderson Revolving Purifier.—This process of purification 
(patented) is in reality a method of adding iron as a coagulant previous 
to subsidence and filtration. The water is passed through a revolving 
cylinder, containing a quantity of iron in the form of turnings or 
punchings, which, as the cylinder rotates, are lifted and scattered 
through the water by means of projections bolted on the inside of the 
cylinder. The inlet and outlet are through hollow trunnions on which 
the cylinder rotates. The rate of flow is such as to give the water 
3 to 5 minutes contact with the iron. The result of the operation is 
that a small amount of the iron is dissolved by the carbonic acid of the 
water, forming ferrous carbonate. On exposure of the water to the air 
in reservoirs, or by artificial aeration, this is oxidized into hydrate 
which acts as a coagulant similarly to aluminum hydrate, in removing 


* Fuller. Water Purification at Louisville, 1898. 







488 MISCELL A NEO US P UR 1 FICA TION PR 0 CESSES. 

color and in aiding sedimentation and filtration (see Chapter XXI), 
An advantage of this process over the use of ferric or aluminum sulfate 
is that no increase in hardness results. 

The amount of iron dissolved is said to be from T V to -J- of a grain 
per gallon. In some waters difficulty has been experienced in getting 
enough iron dissolved to render the process successful. Fuller’s 
experiments at Louisville showed that, as a coagulant, ferric sulfate, 
which contains about 25 per cent of iron, was about equal in value to 
aluminum sulfate. On this basis J grain of metallic iron per gallon 
would be equivalent to 1 grain sulfate of alumina. 

The process has been experimented with in a few places in this 
country, but the results have not led to its adoption. Abroad, more 
favorable results appear to have been obtained. Extensive experi¬ 
ments at St. Petersburg on the water of the Neva, which is naturally 
coffee-colored, showed that this process was competent to remove the 
color, although filtration through asbestos or fine sand did not eliminate 
this somewhat objectionable condition. The waters of the Nile, which 
at flood season carry a large amount of finely suspended clay particles 
that do not settle by ordinary subsidence, when treated by this process 
are quickly clarified. This system is in use at a number of places in 
Europe, notably at Antwerp, Dordrecht, and for some of the suburban 
supplies of Paris. After treatment the water is filtered at a moderate 
rate through sand filters. Recently the benefit of the iron treatment 
over simple filtration has been questioned, and it has been found that 
in some cases the filters have been able to give satisfactory results 
without the preliminary treatment. 

The bacteriological efficiency of the process is high, as would be 
expected from our knowledge of the use of coagulants. Van Ermengen 
found at Antwerp in a water containing 100,000 bacteria per c.c., only 
4 to 6 immediately after filtration. At Paris, tests by Miquel for five 
months (February to July, 1893) gave the following results: 

Seine water, unfiltered.396,000 bac. per c.c. 

Filtered water. 1,702 “ “ 

Reduction per cent. 99-57 

At Boulogne, filtered water contains from 200 to 400 bacteria per 
c.c., which is about y-gVo of the original number. Results of laboratory 
experiments on the Ohio River water at Cincinnati gave the following :* 


* Hill. Public Water-supplies, p. 52. 







DOMESTIC FILTERS. 


489 



Bacteria per c.c. 

1 2 

Before treatment.2304-2832 495-644 

After treatment. .. 50-90 39-119 

The cost of installation is said to be about $5000 per million 
gallons for the plant, exclusive of filters. The cost of operation is 
estimated at $2.00 per million gallons. The depreciation of the 
cylinders would appear likely to be quite high if the action of the water 
upon the iron is effective. 

567. Domestic Filters.—Frequently it is advisable to purify water- 
supplies for household use. For this purpose a large number of 
different filters have been devised, but 
many of these are so inefficient as to 
be worse than useless; for it not in¬ 
frequently happens that the posses¬ 
sion of a filter lulls the consumer into 
a state of false security. The best of 
these filters suitable for household use 
are those that are made of unglazed 
porcelain (Pasteur filter), or fine in¬ 
fusorial earth (Berkefeld filter). 

Filters of this class are compara¬ 
tively porous, thus permitting a fairly 
rapid flow. In this respect the Berke¬ 
feld is superior, as it filters consider¬ 
ably faster than the Pasteur. Both 
of these filters deliver a wholly germ- 
free filtrate when they are first put in 
service, but unless close attention is given them they sooner or later 
lose this property. The pore spaces in filters of this class are not 
smaller than the bacteria that ordinarily abound in the raw water; 
hence the removal of these organisms is not purely mechanical. There 
seems to exist a sort of attraction between the bacteria and the particles 
composing the filter, so that the former are prevented from being forced 
through the pores. This attractive property varies with different 
materials. Guinochet states that the pores in the micro-membranes of 
the asbestos filter made by Breyer are smaller than in the Pasteur filter 
and yet bacteria pass these quite readily. As additional water is 
passed through these filters, the pore-spaces become reduced in size, 
owing to the accumulation of organic or other matter, until finally a 
living pellicle or membrane is formed on the outer filtering surface. 


a 


Fig. 139. —Pasteur Filter. 

a , view from outside. 

b, sectional view. 


































490 


MISCELLANEOUS PURIFICATION PROCESSES. 


This increases the resistance offered to the passage of the water and 
consequently diminishes the flow of the effluent. The bacteria that 
abound in this slimy pellicle are not destroyed, and if the temperature 
is favorable they begin to grow. Under such conditions, the bacteria 
capable of multiplication force their way through the pores of the filter 
and so appear in the filtrate. Filters of this class therefore retain their 
germ-proof qualities for periods that are in a way inversely proportional 
to the temperature of the water. The lower the temperature of the 
water, and therefore the slower the development of the contained 
bacteria, the longer the filtrate will retain its sterile condition. Gen¬ 
erally speaking, these filters should be cleaned and sterilized in boiling 
water or in steam under pressure once a week in order to kill out the 
germ-life that has found lodgment in the pores. In this way not only 
is the sterility of the filtrate maintained, but the yield of filtered water 
is increased. The more rapid rate of filtration in the Berkefeld as 
compared with the Pasteur filter makes this filter lose its efficiency 
more rapidly. 

It is necessary to test the soundness of these filters before they are 
installed. This can be done by-compressing the air in one just after it 
has been boiled and then immersing the same in water. In a perfectly 
sound filter (Pasteur) no bubbles of air should be observed. 

Although it is a demonstrated fact that the normal water bacteria 
will work their way through these filters in the course of a few days to 
a few weeks, still it is by no means so certain that disease organisms 
like typhoid and cholera would do so. Experiments which have been 
made by adding cultures of these organisms to water and then filtering 
the same have shown that these filters kept back the disease bacteria 
for several weeks, but that finally they could be detected in the filtrate. 
When, however, the amount of organic matter added was less, and the 
conditions therefore simulated more nearly those that would obtain in 
a polluted water, the typhoid germ failed to appear in the filtrate.* 

In times of epidemic disease entire reliance should not be placed in 
the operation of these filters, as it frequently happens that some of 
them are defective. An outbreak of 145 cases of cholera in a single 
regiment of 650 men occurred in 1894 in Lucknow, India, as a result 
of an imperfect filter in use in the barracks; but in general the use of 
the best filters has reduced the amount of water-borne disease. This 
is especially noteworthy in the garrisons of the French army, where the 
typhoid death-rate has been much lessened. Rideal mentions an 


* Schofer, Cent. f. Balt., 1893, Xiv. p. 685. 



STERILIZATION AND DISTILLATION. 491 

instance in the barracks at Melun. In 1889 there were 122 deaths 
from this disease; after the introduction of the Pasteur filter, the 
average mortality for the next seven years was only seven. 

Filters of this class are not often used for municipal purification,* 
but are admirably adapted for schools, garrisons, prisons, or hotels as 
well as for private use. 

Other types of household filters, such as those constructed of porous 
stone, charcoal, or asbestos, have been on the market for many years. 
Judged from the popular standpoint of purity, which is generally the 
production of a clear water, many of the filters would be regarded as 
quite satisfactory, but as a means of removing germ-life they possess for 
the most part but little merit. 

568. Sterilization and Distillation.—Not infrequently a public supply 
becomes suspicious and the prudent consumer is forced to protect his 
household by private means. Generally speaking, the introduction of 
satisfactory filters will insure safety if the same are properly managed. 
Another method on which even greater reliance can be placed is the 
use of heat. There are no pathogenic bacteria that are liable to be 
distributed by the way of the water-supply that are able to withstand 
the influence of boiling water for a period exceeding 10-15 minutes. 
Cholera and typhoid succumb in 5 minutes or less. In case of sudden 
outbreaks of disease or temporary disturbance of installed water-sup¬ 
plies, this method can always be relied on with perfect safety. 
There are several types of sterilizers that have been placed on the 
market that are adapted to individual use (see literature); also appa¬ 
ratus that is designed for the treatment of large quantities that would 
be of service in case of epidemics. Ordinarily, measures of this sort 
are left to the option of the water-consumer, but in times of extensive 
epidemics, as in the Hamburg cholera outbreak of 1893, public stations 
supplying sterilized water may be established. Boiling does not, how¬ 
ever, render potable a water containing large amounts of organic 
matter, although it may destroy the disease-germs that may be therein. 
By distillation a water can be obtained free from dissolved matter as 
well as bacteria. This process is extensively used on shipboard to 
obtain potable water from sea-water, and in a few places on the sea- 
coast for similar purposes. In a recent test of a “ triple-effect ” evap¬ 
orator at the Dry Tortugas, Fla., a net distillation of I 3 * 9 ^ pounds of 
water per pound of coal was obtained.t 

* Several cities in India have, however, lately installed filter-plants on this 
system. 

f Eng. News , 1900, xliii. p. 203 




49 2 MISCELLANEOUS PURIFICATION PROCESSES . 

Objection has been raised against the use of distilled water for the 
reason that it contains no salts in solution and hence exerts a powerful 
osmotic effect on animal cells by withdrawing the water from them, 
but its use has not yet been sufficiently extensive to warrant definite 
conclusions. Distilled water is rendered more palatable by aeration 
and the introduction of a small quantity of salt. 

569. Purification by Addition of Chemicals. —There are a consider¬ 
able number of chemical substances that may be added to water in 
order to purify it by carrying down the suspended matter as well as 
bacteria by sedimentation. Such a. process of purification is to be seen 
in the addition of alum, sulfate of iron, and calcium carbonate to water. 
Methods of this character are directly dependent upon the flocculating 
action of the chemical added, and the removal of the bacteria is accom¬ 
plished by subsidence. 

In addition to these methods, a large number of different systems 
have been devised, the effective principle of which rests upon the germ- 
destroying action of some chemical substance, which is later rendered 
innocuous in some way or other. These methods as yet have had only 
limited application, but it must be said that while some of them are 
practically as yet in the experimental stage, they seem to offer rational 
and practicable means of disinfecting water. In times of disease out¬ 
breaks it is entirely possible that methods of disinfection of this class 
would insure greater safety than reliance upon some other methods of 
purification. 

570. Ozone .—Apparently one of the most successful of these 
methods is in the use of ozone which has already been applied on a 
commercial scale. The gas is generated electrolytically and then 
passed through the water. Experiments made by Weyl * on river- 
water such as the Spree, which contained from 16,000-18,000 bacteria 
per c.c., showed a reduction to 100-200 organisms per c.c. The water 
is pumped into a tower and allowed to flow slowly over stones, thus 
bringing it in contact with the air that is heavily charged with ozone. 
The gas acts as a powerful disinfectant, destroying the pathogenic 
organisms with certainty. It is not very readily absorbed by the 
water, hence water treated in this way does not act easily on pipes. 

Weyl claims that even peaty waters may be clarified by this 
process. The compounds of iron and humic acid that cause the brown 
discoloration in the water are oxidized and so disappear. The process 
is said to be economical. In fact Weyl claims that water can be 


* 71. Versammlung deutscher Naturforscher u. Aerzte, 1899. 




THE USE OF CHEMICALS. 493 

treated more economically and with greater efficiency than by sand 
filters.* * * § 

Recently experiments were tried at Lille, Belgium, with the 
apparatus of Marmier and Abraham. Calmette, + reporting these 
results, says that its efficiency is higher than any other known process. 
All pathogenic and other bacteria, with the exception of a few harm¬ 
less spore-bearing hay bacilli, were destroyed. The ozonization of the 
water adds no element prejudicial to health. 

571. Chlorinated Lime J^Fraube s Method ). — In 1893 TraubeJ pro¬ 
posed an exceedingly simple and efficient method of rendering water 
germ-free by the addition of chlorinated § lime or bleaching-powder 
(CaOCl 2 ). This strong disinfectant consists of a mixture of calcium 
hydroxid, Ca(OH) 9 , calcium chlorid, CaCl.,, and calcium hypochlorite, 
Ca(C 10 ) 2 . By virtue of the active chlorine which it contains it will 
destroy all bacteria in a few hours even in extremely dilute solutions. 
The excess of the chlorinated lime may be readily neutralized by the 
addition of sodium sulfite or calcium bisulfite. Water so treated is 
perfectly harmless, and does not have its taste or appearance impaired; 
in fact, remains unchanged except for a slight increase in hardness. 

This method has been tested critically by Bassenge || and Lode,IT 
who have demonstrated its efficiency as a cheap, harmless, and avail¬ 
able method of chemical sterilization of drinking-waters. Either this 
or the preceding method is applicable on a large scale and may be of 
special service in times of epidemic where wholesale treatment is 
demanded. 

572. Peroxide of Hydrogen (H 2 0 2 ).—This disinfecting agent can 
also be utilized in the sterilization of water. In solutions of 1 : 10,000 
the cholera organism is killed in five minutes; the typhoid bacillus in 
one day in solutions of double this strength. In proportions of 1 : 1000, 
water is rendered practically germ-free within 24 hours, and these pro¬ 
portions do not affect the taste. 

A number of other methods have been exploited from time to time 
that involve the use of other chemicals, but no attempts have been 
made on a large scale to utilize them in sterilizing drinking-waters. 


* Cent. f. Bakt ., XXVI. p. 15. 

f Rev. Sci., 4 Ser. xil. p. 432. 

J Zeit. f. Hyg., 1894, xvi. p. 149. 

§ Nissen. U. d. desinficirende Eigenschaft d. Chlorkalks, Zeit. f. Hyg., 1890, 
VIII. p. 62. 

1 Zeit. f. Hyg., 1895, XX. p. 227. 

I} Arch. f. Hyg., 1895, XXIV. p. 236. 




494 


MISCELLANEOUS PURIFICATION PROCESSES . 


LITERATURE. 

SPECIAL FORMS OF FILTERS. 

1. Filtering Plant. “System Fischer und Peters,” at Worms, Germany. 

Eng. News, 1892, xxvm. p. 231. 

2. Schofer. Sandstone-slab Filters on the Fischer System at Worms. Proc. 

Inst. C. E., 1895-96, cxxv. p. 468. 

3. Artificial Sandstone Filters. Eng. Record , 1897, xxxv. p. 515,. 

4. Wilder. The Water-works and Filter-plant at Ripley, N. Y. Eng. 

News , 1898, xxxix. p. 363. Special forms of filter-cells of sand. 

AERATION. 

1. Drown. The Effect of the Aeration of Natural Waters. Report Mass. 

Bd. Health, 1891, p. 385; Eng. News, 1892, xxvm. p. 183. 

2. Brush. Aeration of a Gravity Supply. Proc. Am. W. W. Assn., 1891, 

P- 73 - 

3. Aeration of Charleston, S. C., Water-supply. Eng. Record, 1892, xxvi. 

p. 197. 

4. Aeration in a Water-tank. Eng . Record, 1892, xxvi. p. 296. 

5. Aeration and Continuous Sand Filtration at Ilion, N. Y. Eng. News r 

1894, xxxi. p. 466. 

6. The San Francisco Aerating-plant. Eng. Record, 1896, xxxiv. p. 201. 

SOFTENING. 

1. Latham. Softening of Water. Paper before Soc. of Arts. Of historical 

value. Eng. Neivs, 1885, xm. p. 65. 

2. Matthews. The Southampton Water-works and Softening Plant. Proc. 

Inst. C. E., 1891-92, cviii. p. 285. 

3. Softening Hard Water for Locomotive Use. Eng. News, 1892, xxvn. 

p. 578. 

4. Atkins. Water Softening and Scientific Filtration. London, 1894. 

5. Collet. Water Softening and Purification. London, 1895. 

6. Purifying Water for Locomotive Boilers. Eng. News, 1896, xxxv. 

p. 406. 

7. Archbutt. Water Softening. Proc. Inst. M. E., 1898, p. 404. 

Abstract, Eng. News, 1898, xl. p. 403; Eng. Record, 1898, 
xxxviii. p. 388. 

8. Stillman. A Water-purifying Plant. Trans. Am. Soc. M. E., 1898, 

xix. p. 415. Description of a plant for purifying locomotive feed- 
water. 

9. Recent Practice in Purifying Feed-water for Locomotives. Report of 

Com. of Mast. Mech. Assn. Eng. News, 1899, xli. p. 411. 

10. Goldsmith. Water Softening at Lorain. Paper before Am. Soc. M. E. 
Abstract, Eng. Record, 1900, xli. p. 472. 

REMOVAL OF IRON. 

1. Wellmann. Ueber Beseitigung des Eisengehaltes im Grundwasser mit 
Beziehung auf die Chariottenburger Wasserwerke. Jour. f. Gas. u. 
Wasservers., 1894, xxxvn. p. 595; Eng News, 1895* xxxiv. p. 147. 


LIT ERA TURK . 495 

2. Pippig. Die Grundwasser-Enteisenungsanlage des Ivieler Wasserwerks. 

Jour. f. Gas. u. Wasservers., 1896, xxxix. p. 650. 

3. Removal of Iron from Ground-water at Reading, Mass. Eng. News , 

1896, xxxvi. p. 348. 

4. The Removal of Iron from Artesian Well-water by Mechanical Filtration. 

Eng. News , 1896, xxxv. p. 364, 

5. Dunbar. On the Nature and Treatment of Ferruginous Subsoil Water. 

Zeitschrift fur Hygiene, 1896, p. 68. 

6. Clark. Removal of Iron from Ground-waters. Jour. New Fng. W. W. 

Assn., 1897, xi. p, 277. 

7. Bancroft. The Iron-removal Plant at Reading, Mass. Jour. New Eng. 

W. W. Assn., 1897, xi. p. 294. 

8. The Removal of Iron from Ground-water. Eng. Record , 1899, xl. 

p. 412. Describes several plants. 

9. Iron Removal from Ground-water at Far Rockaway by Slow Sand Filtra¬ 

tion. Eng. News , 1900, xliii. p. 238. 

10, Uber freiwillige Eisenausscheidung a. Grundwasser u. eine Enteisenungs- 

methode f. Kesselbrunnen. Zeit. f. Hyg., xx. p. 397. 

11, Uber d. Grundwasser von Kiel mit besonderer Berticksichtigung seines 

Eisengehaltes u. iiber Versuche z. Entfernung d. Eisens. Zeit. f. 
Hyg., xiii. p. 251. 

12, Uber die Natur und Behandlung eisenhaltigen Grundwassers. Zeit. L 

Hyg., xxii. p. 68. 


ELECTRICAL PROCESSES. 

1. The Rorske System of Water Purification. Eng. Record , 1893, xxvnu 

p. 282. 

2. Sewage Purification in America; Electrical Treatment at Brewsters, N. Y, 

Eng. News , 1893, xxx. p. 41. 

3. Drown. The Electrical Purification of Water. Jour. New Eng. W. W. 

Assn., 1894, p. 183. 

4. Napier. The Hermite Process of Deodorizing Sewage. Paper before 

British Assn. Sci. Am. Sup., Nov. 1895, p. 16565. 

THE ANDERSON PROCESS. 

1. Anderson. The Antwerp Water-works. Proc. Inst. C. E., 1882-83, 

cxxii. p. 24. 

2. Anderson. The Purification of Water by Means of Iron on the Large 

Scale. Proc. Inst. C. E., 1884-85, lxxxi. p, 279. 

3. Ogston. The Purification of Water by Metallic Iron in Mr. Anderson’s 

Revolving Purifiers. Proc. Inst. C. E., 1884-85, lxxxi. p. 285. 

4. Devonshire. The Purification of Water by Means of Metallic Iron. 

Jour. Franklin Inst., 1890, cxxix. p. 449. 

STERILIZATION BY CHEMICALS. 

1. Traube. Einfaches Verfahren Wasser in grosser Mengen keimfrei zu 

machen. Zeit. f. Hyg., xvi. p. 149. 

2. Schumburg. Ein neues Verfahren z. Herstellung keimfreien Trinkwassers 

[Bromine water]. Deutsche med. Wochenschr., 1897, No. 10; also 
ibid. , 1897, No. 25. 


496 MISCELLANEOUS PURIFICATION PROCESSES. 

3. Bassenge. Zur Herstellung keimfreien Trinkwasser durch Chlorkalk. 

Zeit. f. Hyg., xx. p. 227. 

4. Soper. The Purification of Drinking-water by the Use of Ozone. Eng . 

News , 1899, xlii. p. 250. 

5. Soper. The Ozonization of Water. Jour. New Eng. W. W. Asssn., 

1 goo, xv. p. 1. 

6. Weyl. Ueber die Verweridung von Ozone zur Gewinnung keimfreien 

Trinkwassers. Jour. f. Gas- u. Wasservers., 1899, ■ xlii. p. 809; 
also Cent. f. Bakt., xxvi. p. 15. Abstract, Eng. News , 1900, xliii. 
p. 92; Eng. Record, 1900, xli. p. 105. 

HOUSEHOLD FILTERS. 

1. Kiibler. Unters. ii. d. Brauchbarkeit der “ Filter sans pressions, Systeme 

Chamberland-Pasteur.” Zeit. f. Hyg., vm. p. 48. 

2. Nordtmeyer. U. Wasserfiltration durch Filter aus gebrannter Infusorien- 

erde. Zeit. f. Hyg., 1891, x. p. 145. 

3. Breyer. Hyg. Rundschau, 1891, p. 977. 

4. Th. Weyl. Berl. klin. Wochenschrift, 1892, No. 23. 

5. E. von Esmarch. Uber Wasserfiltration durch Steinfilter. Cent. f. Bakt., 

1892, xi. p. 525. 

6. Kirchner. Unters. ii. d. Brauchbarkeit der “ Berkefeld Filter” aus 

gebrannter Infusorienerde. Zeit. f. Hyg., 1893, xiv. p. 299. 

7. Gruber. Gesichtspunkte f. d. Priifung u. Beurtheilung v. Wasserfiltern. 

Cent. f. Bakt., 1893, xiv. p. 488. 

8. John. Einige Untersuchungen ii. d. Leistungsfahigkeit d. Kieselguhr- 

Filter. Zeit. f. Hyg., 1894, xvn. p. 517. 

STERILIZATION BY HEAT. 

1. Treatment of large quantities of water. Berl. klin. Wochensch., 1892, 

p. 663. 

2. Laser. Expts. made with the Dessauer Sterilizer. Cent. f. Bakt., 1803, 

xiv. p. 749. 

3. Rubner and Davids. Tests of von Siemens’ Apparatus. Berl. klin. 

Wochensch., 1893, p. 861. 

4. Schultz. Expts. with Werner von Siemens’ Apparatus. Zeit. f. Hyg., 

1894, xv. p. 206. 




C WORKS FOR THE DISTRIBUTION OF WATER. 


CHAPTER XXIV. 

PIPES FOR CONVEYING WATER. 

\ 

573. Materials Employed.—A variety of materials may be employed 
for the construction of water-conduits. If the conduit is not under 
pressure, the form of construction used may be an open canal dug in 
the natural earth, or a masonry conduit in “cut and cover,” or a 
tunnel. Where the water flows under pressure the first two types are 
not suitable and a pipe, or possibly a tunnel, must be employed. The 
method of construction used in connection with canals, masonry con¬ 
duits, and tunnels will be described in the next chapter; the present 
chapter will deal only with the design and manufacture of pipes. 

The materials used for water-pipes are cast iron, wrought iron, 
steel, wood, cement, vitrified clay, lead, and occasionally a few other 
materials. The important requirements for a water-pipe are strength, 
durability, and low cost. The relative importance of these require¬ 
ments will vary under different circumstances, and this will lead to the 
use of different materials in different cases. 

574. Stresses to be Considered.—The stresses to be considered in 
the design of water-pipes are those due to (1) the water-pressure, (2) 
the pressure of the surrounding earth and the action of other outside 
forces, (3) changes of temperature, and (4) blows and shocks received 
in transportation and construction. 

575. Stresses Due to Water-pressure .—The maximum pressure to 
be provided for will be the maximum which can occur under normal 
conditions of operation (usually the maximum possible static pressure), 
plus an allowance for water-hammer. The former can readily be 
computed, but the latter is difficult of estimation. 

Sometimes pipe-lines are so designed that static pressure can never 
occur, the valves being so arranged that the water never comes to rest. 

497 



498 PIPES FOR CONVEYING WATER. 

In that case the maximum pressure at any point will be the maximum 
pressure-head which can exist under the assumed conditions of flow. 
This will be less than the static head by the amount lost in friction 
from the open end of the pipe to the point in question. (See further 
discussion in Art. 630.) 

The dynamic effect, or the amount of water-hammer to be assumed 
depends on many circumstances. It was shown in Chapter XII that 
it varies in general with the length of the pipe, with the velocity of the 
water, and with the rapidity with which the velocity is changed by the 
action of valves or otherwise. The amount to be allowed should 
evidently be varied according to the nature of the pipe-line. 

In a distributing system of small pipes where the operation of 
hydrants and large branches has a relatively great influence on the 
system, the allowance should be large. In this case the amount added 
for water-hammer has commonly been about 100 pounds per square 
inch, which, from the theoretical considerations of Chapter XII would 
appear to be quite high enough for all ordinary cases. The amount 
assumed for cast-iron pipes in the new pipe system of the Metropolitan 
Water-works of Boston is given on page 502. 

In the case of a large pipe-line without branches, and carefully 
protected from excessive pressure by relief-valves and by precautions 
in operating shut-off valves, the allowance for water-hammer need be 
very little, especially for pipes of steel or wood. It is true that any 
reduction whatever in velocity, due to the closing of a valve, will raise 
the pressure an amount proportional to the length of the pipe affected, 
the velocity of the water, and inversely as to the time required in 
closing. For example, if a stop-valve of a 48-inch pipe be closed in 
60 seconds, the average pressure with four miles of pipe-line would be 
14 pounds per square inch. Large wooden and steel pipe-lines are 
commonly designed with little or no allowance for hammer, but foi 
those portions under light pressure it would be well to make an allow¬ 
ance of 25 to 50 pounds, depending on the velocity of the water and 
the length of pipe involved. For those portions of the pipe under heavy 
pressure the ram would be small in proportion to the static pressure, 
and the necessity for considering it would be less. 

The intensity of the circumferential stress in a circular pipe is 


where r — radius of pipe, 

p — pressure-head, and 
/ = thickness of shell. 



STRESSES IN PIPES. 


499 


Water-pressure must be specially considered at sharp curves and 
angles. At such places the pressure tends to displace the pipe-line 
and force the pipes apart. 

576, Stresses Due to Earth Filling and Other Outside Forces .— 
The pressures due to the forces here considered tend to collapse the 
pipe. The effect of earth filling will be felt seriously only for very 
deep trenches and for large pipes, while the effect of traffic is of impor¬ 
tance only for very shallow filling. To protect pipes from injury due 
to traffic a minimum depth of covering of 2 to 3 feet will usually be 
sufficient, since the pipes themselves are able to sustain a very con¬ 
siderable load if it is distributed. The stresses caused by heavy loads 
of earth need to be more fully considered, and a rough analysis of the 
problem will be of some assistance. 

If we neglect the lateral support of the earth and assume the weight 
of filling applied as a vertical load, uniformly distributed over a width 
equal to the diameter of the pipe, and 
assume also the upward pressure 
against the pipe to be similarly ap¬ 
plied, there will be produced equal 
bending moments at a and b (Fig. 

140), but of opposite sign.* If W = 
total load and d — diameter of pipe, 
the bending moment at these points 
will therefore be 



Print 


¥ 

P 

i 

& 




IS. 


Fig. 140. 


M= T \Wd. 


Assuming h = depth of fill in feet; weight of filling = 100 pounds 
per cubic foot; f — safe fibre-stress in bending for the pipe material; 
d = diameter of pipe in inches; and t — thickness of pipe in inches, 
we derive, from the ordinary beam formula, approximately 


t = 



\ 

If, for example, we assume for cast iron a value o tf= 7000 pounds 

per square inch, we will have t — .00 6d Vh. Thus for a 48-inch cast- 
iron pipe, and a depth of filling of 16 feet t — 1.15 inches, and for a 



* Because a similar set of horizontally applied forces must reduce the moments 
at a and b to zero. See also a paper by Wm. H. Searles on “ Deflections and Strains 
in a Flexible Ring under Load.” Jour. Assn. Eng. Soc., 1895, xv. p. 124. 






PIPES FOR CONVEYING WATER. 


5 CO 

depth of 25 feet t — 1.44 inches. The smaller of these values is about 
as small as would be used in any case for this size of pipe. 

This analysis is of course very rough, but it serves to give some 
notion of the maximum stress that is possible from earth pressure. It 
is to be noted that we have here entirely neglected the lateral pressures 
involved. In the case of cast-iron pipe the material is so rigid that 
the lateral support received by the earth may be very little and the 
load will be supported largely through the bending resistance of the 
pipe; but if the pipe is relatively flexible, like steel or even a wooden- 
stave pipe, it will get much aid from this lateral pressure, especially if 
the earth is well tamped in place. Cases of the breakage of cast-iron 
pipe under high embankments have occurred, but the above analysis 
indicates that usually no account need be taken of earth pressures when 
the depth of filling is less than 10 or 15 feet. 

In the case of large steel pipes built of comparatively thin material 
stiffening-rings are sometimes used to support heavy loads, as, for 
example, on the large Brooklyn line, where stiffening-rings of 4 X 4 X 
f-inch angles were used under all waterways and wherever the covering 
exceeded 6 feet. A covering of concrete is also sometimes employed 
to give additional strength. In most cases, however, no trouble will 
be had if the back-filling is well tamped, and the pipe perhaps tem¬ 
porarily supported by interior braces. Where the filling is not well 
done steel pipes have been greatly flattened at the top by the load of 
earth. At Portland, Oregon, a flattening of 4 inches was caused in this 
way. Experiments there made showed, however, that a distortion of 
as much as 8f inches in a 42-inch steel pipe caused no leaks, although 
a flattening of only if inches caused a permanent set of f inch.* 

Experiments on a 61-inch cast-iron pipe, ij inches thick, for the 
Sudbury conduit, showed a difference of from .005 to .01 foot between 
horizontal and vertical diameters due to deflection from its own weight 

o ‘ 

and a maximum deflection of .015 foot under a load of 4 feet of 
gravel, t 

Another possible outside force which should be considered in the 
design is the unbalanced pressure due to the creation of a partial 
vacuum when emptying the pipe. The capacity of the air-valves 
should be made such as to preclude dangerous pressures from this 
source. 

577. Stresses Due to Temperature Changes .—If no expansion or 


* Trans. Am. Soc. C. E., 1897, xxxvm. p. 93. 
f Eng. Record , 1898, xxxvm. p. 51. 





CAST-IRON PIPE. 


501 


contraction is allowed in a pipe-line, the longitudinal stresses due to 
changes of temperature will be equal to 


s — ETc ... (3) 

where s = intensity of stress; 

E — modulus of elasticity; 

T — change of temperature; 
c = coefficient of expansion. 

Temperature stresses, as a rule, need not be considered except in 
the case of riveted steel pipe. (See Art. 593.) 

578 . Stresses Caused in Transportation and Construction .—Such 
materials as cast-iron and vitrified pipe require a considerable thick¬ 
ness to provide for these stresses. The necessary allowance for this 
purpose has been determined by practical experience, and account of 
it is taken in the formulas and rules for thickness. 


CAST-IRON PIPE. 

579. General—Cast iron is the most widely used material for water- 
pipe. By reason of its moderate cost, its durability, and the conve¬ 
nience with which it may be cast in any desired form it is almost 
universally employed for the pipes and various special forms of distrib¬ 
uting systems. It is also frequently employed for large pipe-lines, 
and is now easily obtained in any desired diameter up to 6 feet or 
more. Cast-iron pipes are made in lengths of about 12 feet, which are 
joined together usually by the bell-and-spigot joint run with lead. 
Branches and other irregular forms are used for connections. These 
are called special castings, or simply “specials.” 

580. Thickness and Weight of Cast-iron Pipe.—The material used 
for pipes is usually required to have a tensile strength of from 16,000 
to 18,000 pounds per square inch. A factor of safety of 5 may be 
assumed where proper allowance is made for water-hammer. In 
addition to the thickness required to sustain water-pressure a small 
addition must be made to allow for eccentricity of casting and to pro¬ 
vide sufficient strength to bear transportation. One-tenth of an inch 
should be sufficient for the first allowance. For the second object it 
would seem that no allowance at all need be made for such sizes and 
pressures that the thickness required to sustain the water-pressure 
would be large. However, it is customary to make some allowance 



502 


PIPES FOR CONVEYING WATER. 


for all sizes. The total amount allowed for both the above-mentioned 
objects varies in the different formulas from about .25 to .35 inch. 

Different formulas are used by different pipe-foundries and by dif¬ 
ferent cities in determining the thickness of pipe. A formula which 
commends itself as being simple in form and rational in its make-up 
is that used by the Metropolitan Water-works of Boston. It is 


t 


(P + P')r 

3300 


+ 0-25, 



where t — thickness in inches; 

p — static pressure in pounds per square inch; 
p' = allowance for water-hammer in pounds per square inch; 
r = radius of pipe in inches; 

0.25 = allowance for eccentricity, deterioration, and safety in hand¬ 
ling. 

The value of/' is to be taken as follows: 


Size of Pipe. Value of 

3-in. to io-in. 120 

12-in. no 

16-in. 100 

20-in. 90 

24-in. 85 

30-in. 80 

3 6 “ in . 7 5 

42-in. to 60-in. 70 


This formula assumes a strength of 16,500 pounds per square inch 
and a factor of safety of 5. It gives pipe somewhat thinner than that 
formerly used by the Boston Water-works, and about as light as it is 
advisable to use. It properly varies the allowance for water-hammer 
according to the size of pipe. 

Large cities usually adopt a few standard thicknesses for each size, 
corresponding to certain pressures, the pipes designed for the different 
pressures being designated as Class A, Class B, etc. The variations 
between classes usually correspond to a difference of pressure of about 
50 pounds per square inch. The various pipe-foundries have likewise 
their standard weights for different sizes, which differ more or less 
among themselves and also differ from the various city standards. For 
large orders of pipe it is easy to secure any designated weights, but for 
small orders it will be economy to select from the standards given in 
the manufacturers’ lists that weight which will come nearest to the 
weight desired. 












CAST-IRON PIPE. 


503 


The minimum practicable thicknesses for the various sizes of pipes 
correspond to a pressure of about 40 pounds per square inch if eq> (4) 
be used. These minimum thicknesses are about as follows: 


Size of Pipe. 

4-in... 
6 - to 8-in 
10-to 12- “ 
14-to 16- “ 
18-in. . 
20- “ . 
24- “ . 


Minimum Thickness. 


I in. 

7 “ 

Iff 

i “ 

9 “ 

Iff 

• i “ 

ii“ 

Tff 

I “ 


fSize of Pipe. 

Minimum Thickness 

30-in. 

is ; n 

36- “_ 

7 “ 



42- to 48-in. . 


54 -in. 

.I* “ 

60- “ _ 

.I± “ 

72-“ .... 

.I* “ 


In Table No. 74 are given the thicknesses for various pressures as 
deduced from eq. (4), also the average weight per foot, and the total 
weight of 12-foot lengths, as employed by the Metropolitan Water¬ 
works. 


TABLE NO. 74. 

THICKNESS AND WEIGHT OF WATER-PIPE USED BY THE METROPOLITAN WATER-WORKS 

BOSTON. 


C/5 

<v 

-jg 

U 

c 


u 

<v 

*-> 

B 


4 

6 

8 

10 

12 

14 

16 

20 

24 

30 

36 

42 

48 

54 

60 


Class A. 
115 -foot Head. 


v 

X 

w _ 
l/> c 

c — 

X OJ 

.w X 
j- m 

H 


0-93 
1.01 
I-I5 
I.23 
1-35 


X! 

bp 

'v 

^ o 
V o 
Ufa 
, 

U. ^ 

> a 

< 


be 

a 

<4-1 V 

0_) 

t*-? 

:s 2 


366.7 

467-5 

605.8 

730.8 

885.8 


Class B. 
150 -foot Head. 


t/i 

<u 

X! 

o c 

to 

to G 

<y ■- 

C s 

Ujs 

X|C /3 

H 


4400 

5610 

7270 

8770 

10630 


0.57 
o. 61 
0.65 

0.73 

0.S0 
0.92 
1.03 
1.14 
1.25 
i-35 
1.50 


xs 

m bp 

'5 

^ o 
V o 
W 
2 u 
<v <v 

> ex 

*< 


75 

94 

ii 5 

160 

210 

302 

404 

524 

655 

797 

979 


h£ 

e 

Vi V 

«-• . 

X -V. 

be'v 
•71 « 


910 

1130 

1380 

1930 

2525 

3625 

4850 

6290 

7870 

9570 

11750 


Class C. 
200 -foot Head. 


CO 

V 

X 

°>5 

" e 

CD —■ 

X V 
OJ 3 

X & 

H 


.61 

65 

.70 

•79 

•87 

,00 

13 

27 

40 

■53 

70 


'5 

^ o 
(U o 
b£tL, 
rt . 

V. >- 
<U o 

> a 


80.8 
100. o 

123.7 

173-3 

228.3 

327-5 

441.7 

581.2 
730.0 

919.2 

1132.5 


be 

X! -J 

u-r 


970 

1200 

1485 

2080 

2740 

3930 
5300 
6975 
8760 
11030 
13590 


250 

Class D. 

-foot Head. 

300 

Class E. 

-foot Head. 

Thickness of 

Shell in Inches. 

1 

Average Weight 
per Foot. 

Weight of 

12 -ft. Length. 

Thickness of 

Shell in Inches. 

Average Weight 
per Foot. 

Weight of 

12 -ft. Length. 

O.40 

19.2 

230 

0-45 

21.2 

255 

O.46 

31-7 

380 

O. 50 

34-6 

415 

O.52 

47.I 

565 

0-55 

50.0 

600 

O. 60 

66.7 

800 

0.63 

70.0 

840 

O.65 

85.8 

1030 

0.69 

91.2 

1095 

O.70 

107-5 

1290 

0-75 

115.0 

1380 

0-75 

I32.5 

1590 

O.81 

I42.9 

1715 

0.85 

186.2 

2235 

O.92 

201.2 

2415 

0-95 

248.7 

2985 

I.03 

269.2 

3230 

I. IO 

361.2 

4335 

1.20 393.3 

4720 

1.25 

I.40 

1-55 

491.7 

645.8 
818.3 

5900 

7750 

9820 

I.36 

533*3 

6400 


581. Joints. — The Ordinary Bell-and-spigotJoint. —The joint which 
is ordinarily employed in this country is the bell-and-spigot joint. 
The space between bell and spigot is filled with lead, which is calked 
solidly into place so as to be water-tight. Many forms of bell or 
socket have been devised, but practice has come to be quite uniform 








































































5°4 


PIPES FOR CONVEYING WATER . 


on this point, as is illustrated by Fig. 141, which shows the forms of 
spigot used in several cities. The chief requisites of a bell and spigot 
are: 1st, sufficient space to allow of thorough calking, but no more 
space than necessary; 2d, sufficient depth of bell to enable a tight 
joint to be made and to give considerable lateral strength to the pipe; 
3d, sufficient strength of bell to resist the bursting-force due to calk- 



Chicago. Brooklyn. 




Fig. 141.—Standard Forms of Bell-and-spigot Joints. 


ing. It will be noted from the illustrations that a groove of some sort 
on the interior of the bell is now the general practice. This is for the 
purpose of holding the lead more firmly in place. The interior sur¬ 
face of the pipe at the joints should be as smooth as possible. In the 
case of some large pipe recently laid, the joints on the interior of the 
pipe were filled with Portland-cement mortar in order to give a smooth 
surface. 

In Table No. 75 are given the various dimensions of standard bell 
and spigot of the Metropolitan Water-works, Boston (Fig. 142), to¬ 
gether with amounts of lead and packing required per joint. 

The ordinary bell-and-spigot joint with lead packing will enable 
pipes to expand and contract under moderate changes of temperature 
such as occur with buried pipes. 

Curves of large radius can be constructed with straight pipe by 
deflecting each length slightly. In this way it is possible, with a 
reasonable deflection, to lay 4- to 8-inch pipe to a curve of 150-foot 
radius, a 16-inch pipe to a 250-foot radius, and a 36-inch pipe to a 
500-foot radius. 












































CAST-IRON PIPE . 


505 




OPSi 



IAS 


-Z?.--.>1 

Fig. 142.—Standard Bell and Spigot, Metropolitan Water-works, Boston. 


TABLE NO. 75. 

DIMENSIONS of standard bell and spigot, metropolitan water-works, 

BOSTON (FIG. 142). 


Size of 
Pipe. 

Class. 

Dimensions in Inches. 

Average Wt. of 
Lead per Joint. 

Weight 
of Jute 
Gasket 
per 
Joint. 

A 

B 

c 

D 

J 

With 

Gasket. 

Solid 

Lead, 

4 

All classes 

1.50 

I.30 

0.65 

3-00 

0.40 

7 

9 t 

. IO 

6 


4 4 

I.40 

0.70 

4 4 

4 4 

9 f 

I2f 

•15 

8 


i 4 

1.50 

0.75 

3-50 

4 4 

12^ 

i8f 

•25 

10 

4 4 

4 4 

4 4 

< 4 

4 4 

4 4 

T 5 i 

23I 

•30 

12 


4 t 

I.60 

0.80 

14 

4 4 

18 

27 

•35 

14 

t i 

4 4 

1.70 

O.85 

4 4 

4 4 

2 °i 

3 i 

.40 

16 

i ( 

1-75 

I.80 

O.9O 

4-00 

0.50 

3 ii 

5 °t 

•65 

20 


4 t 

2.00 

I .OO 

4 4 

4 

38 i 

62 

. 80 

24 

4 i 

2.00 

2 . IO 

1.05 

4 4 

4 4 

45-2 

74 

•95 

30 

B and C 

< i 

2.-30 

1 • 15 

4.50 

4 4 

56 

I0°| 

i-55 

30 

D and E 

< 4 

2.50 

I.25 

i 4 

4 4 

57 

102 

4 4 

36 

A, B, f nd C 

4 < 

4 4 

4 4 

4 4 

44 

67 

1 20^ 

1-85 

35 

D and E 

t i 

2.80 

I.40 

4 4 

4 4 

68 £ 

I22| 

4 4 

42 

A, B, and C 

< 4 

4 4 

4 4 

5-oo 

4 4 

ll\ 

154 

2.6g 

42 

D 

i < 

3.20 

1.60 

4 4 

4 4 

78 b 

156 

4 4 

48 

A, B, and C 

4 4 

3.00 

1.50 

4 4 

4 4 

m 

176 

3-00 

48 

D 

2.25 

3-50 

i -75 

4 4 

4 4 

891 

178 

• 4 

54 

A and B 

(c 

3.10 

i -55 

5-50 

4 4 

99 i 

215 

3.95 

54 

C 

4 4 

3-90 

i *95 

4 4 

4 4 

100 

2 i 5 i 

4 4 

60 

A and B 

i « 

3.20 

1.60 

4 4 

4 4 

iiof 

239 

4.4O 

60 

C 

4 4 

4.20 

2.10 

4 4 

4 4 

in 

241 

4 4 


582. OtJier Forms of Joints .—In England and at a few points in 
this country the bored and turned joint has been used. A form ol 
this type of joint is shown in Fig. 143. The in¬ 
side of the socket and outside of the spigot are 
turned to an accurate fit, and the joint is made 
by simply driving the pipes together by means of 
a wooden ram. Sometimes cement filling is used 
in addition. In some cases the cost of boring 
and turning is reported to be less than that of 
lead joints, while in other cases the opposite is 
true. A difficulty experienced with this type of joint is in the drawing 
apart of the pipes from temperature changes. 



Fig. 143, 
Turned Joint. 

























































5C6 


PIPES FOR CONVEYING WATER. 



Wooden wedges have been employed to a limited extent in place 
of lead packing. At Yarmouth, Nova Scotia, such joints have been in 
use since 1851, and have proven so durable that they have recently been 
adopted as the standard for that place. The wedges are made from 
clear, dry, pine staves. The cost is stated to be from 6 to 13 cents 
per joint for sizes from 8 to 24 inches in diameter. Joints of this sort 
have been found in perfect condition after a lapse of from forty to forty- 
five years.* This form of joint would probably be advantageous where 
electrolysis is to be feared. 

A joint that has been used somewhat in Europe, and which is espe¬ 
cially suitable for temporary work, is made by means of a solid rubber 
ring. The ring is inserted in the socket near the outside edge and is 
rolled back by pushing the pipe into place. For this joint a smooth 
bell would be preferable. Other forms of rubber joints have been 
employed occasionally, sometimes for expansion purposes. (Art. 641.) 

For inside work and connections in confined locations the flanged 
joint is more convenient than the bell and spigot. It is also better 
suited for temporary work. The flanges are faced carefully at right 
angles to the axis of the pipe, and the joint is bolted together with rub¬ 
ber or other packing between the flanges. Various standards are used 
for proportioning the flanges, as to thickness,'number of bolts, etc., 
for which reference may be made to the various trade circulars, t 

For joining pieces of pipe a sleeve is used, which is essentially a 
short piece of pipe with two bells. It is illustrated in Fig. 144. 
When a pipe is cut to make a connection it is usual to shrink a small 
half-oval or semicircular band on the end to take the place of the rib 
which forms the ordinary spigot. 

583. Special Castings.—The ordinary special castings required are 
the J, -J, and bends or curves, T’s and crosses, or three-way and 
four-way branches, Y branches, blow-off branches, offsets, sleeves, 
caps, and plugs. The various forms are illustrated in Fig. 144. Many 
of the larger cities have their own standard designs for specials as well 
as for straight pipe, which differ more or less from the manufacturers" 
standards. For the smaller cities it will be much the more econom¬ 
ical to use either the manufacturers’ standards or those of some neigh¬ 
boring large city. 

The various branches are manufactured either with part bell and 
part spigot ends, or with all bell ends. The latter form is usually 

* Jour. N. E. Water-works Assn., 1900, xv. p. 34. 

t See also standard proposed by the Am. Soc. M. E. in Trans. Am. Soc. M. E., 
1893, xiv. p. 48. 





CAST-IRON PIPE . 


507 


prefci 1 ed foi branches, as it enables connections to be readily made by 
means of pieces of pipe. 

In designing special castings consideration should be given to the 
fact that such castings cost, as a rule, about twice as much per pound 
as straight pipe. They should therefore be as light and compact as 



£ Bend. i Bend. 



Reducer. 



Offset. 



Cap. 



Four-way Branch. 



Blow-off Branch. 


Fig. 144. —Special Castings. 




Sleeve. 


practicable. They are made of the same thickness as the corresponding 
straight pipe, but with a less number of variations for the different pres¬ 
sures. The general form of specials should be such as to cause as 
little disturbance in the water in passing around angles, etc., as prac¬ 
ticable. This is of considerable importance where the velocity is high, 
and hence should be carefully considered in the design of hydrants and 
hydrant branches. 










































5o8 


PIPES FOR CONVEYING WATER. 



584. Material and Method of Manufacture.— Quality of Iron .— 
Water-pipe should be made of the best quality of gray iron, uniform in 
grain and soft enough to be readily worked. The metal should be 
made without the admixture of cinder-iron or other inferior metal, and 
no ordinary scrap should be used in the manufacture. A mixture of 
pig irons is usually required to give the best results, the proper propor¬ 
tions being a matter of experience. An ordinary specification for the 

strength of the material is that a 
test-bar 2 inches by 1 inch in cross- 
section, placed on supports 24 
inches apart, shall sustain a load 
of 1900 pounds at the center, and 
shall have a deflection of at least 
t 3 q- inch before fracture. This re¬ 
quirement insures a certain amount 
of toughness, or resilience, as well 
as strength. Frequently a tension- 
test is required, the ultimate 
strength specified being from 16,- 
000 to 18,000 pounds per square 
inch. It should be specified that 
test-bars shall be poured at any 
time during the day that the in¬ 
spector desires. 

585 . Molding and Casting .— 
Water-pipes are now always cast 
in vertical molds, and should be 
required to be cast with the bell 
end down, except, perhaps, for the 
smaller sizes. The form of mold 
used is shown in Fig. 145. The 
cores are made by winding the 
socket-ring D and the spindle C 
with hay rope, then coating with 
damp sand and shaping in a 
lathe. Much care is required in 
molding and casting to secure good results, and in spite of the greatest 
care much pipe will need to be rejected if the inspection is properly 
done. In the case of a contract of any considerable size the city should 
always employ a competent inspector to protect its interests. 

Cores should be accurately centered so that the shell will be of 


A , Flask. B, Base. 

C Spindle. E), Socket. 

E, Roping. E } Bead ring. 

J, Sand. 

Fig. 145. —Pipe-mold. 

(From Cassier's Magazine , vol. vm.) 
























































CAST-IRON PIPE. 


509 


uniform thickness, and the bells and spigots should be truly circular. 
The pipe should be free from all surface imperfections that will weaken 
it or lessen its durability, such as checks, blow-holes, sand-holes, and 
cold-shuts; and should be smooth and free from lumps, scales, blis° 
ters, etc. No plugging of blow-holes or the like should be permitted. 
Care should be taken to have the core a$ smooth as possible, and firm 
enough to support the metal. It frequently happens that ridges are 
formed on the interior of the pipe, due to the compression of weak 
cores. The smoothness of the interior is specially important in order 
that the resistance to the flow of water may be a minimum. Specials 
should be true to the designated form. 

After casting, the pipe should be allowed to cool before being 
taken from the molds, in order to prevent unequal contraction. As 
soon as the pipe is uncovered it should be thoroughly cleaned of sand 
by means of wire and other brushes, and should then be inspected for 
surface imperfections and for thickness and form. To detect surface 
defects the inspector uses a light, pointed hammer, and for measuring 
the thickness calipers are applied to the pipe at several points, an 
allowance of from to yL inch being made for variations from the 
exact specified dimensions. The forms of the sockets and spigots are 
tested by templates. Defective spigots are often cut off in a lathe and 
a new spigot made as described on page 506. A small percentage 
of such defective pipe is usually allowed by the specifications. Each 
piece of pipe should have cast upon it a serial number to designate 
the number of the cast and the year, and also letters to designate the 
manufacturer. 

586. Coating .—To prevent rapid deterioration, all pipe should 
• receive some sort of protective coating. The first successful process 
for coating was invented by Dr. Angus Smith in 1849, ancl was intro¬ 
duced into the United States in 1858 by Mr. Kirkwood. This coating 
was composed of a varnish of coal-tar and linseed-oil. The ordinary 
coating as now used is commonly called the Angus Smith coating, but 
it differs considerably from that originally employed. As now applied 
in practice it usually consists of ordinary coal-tar, or distilled tar with 
dead-oil added to give fluidity to the material. Sometimes resin or 
creosote is added. In the process of coating, the tar is maintained at 
a temperature of about 300 degrees Fahrenheit. The pipe is also 
usually heated to about the same temperature before dipping, but is 
sometimes dipped cold and allowed to remain in the bath until it 
acquires the same temperature as the tar. Some specifications require 
the pipe to be removed and then redipped in order to give a thicker 


5io 


PIPES FOR CONVEYING WATER. 


coating. When cool the coating should be hard, tough, and smooth, 
and should not loosen under the blows of a hammer. 

To obtain good results the pipe must b'e absolutely clean and free 
from rust before dipping; otherwise the tar will not adhere to the iron. 
It is supposed that most of the corrosion which appears in the interior 
of the pipe starts at a point where there is some minute defect in the 
coating, and it is therefore very important that the coating be con¬ 
tinuous. In some recent work done in Boston the interior of the pipe 
has received an additional coating of paraffine or vulcanite applied 
with a brush, in the hope that, any minute holes in the coating would 
be filled. Any injury which occurs in handling should be remedied by 
the application of some kind of asphalt paint or tar varnish. 

Asphalt has been tried in various ways as a coating for cast-iron 
pipe, but without much success. It does not appear to adhere as firmly 
as tar. 

587- Testing and Weighing .—After coating, each section of pipe 
should be subjected to an hydraulic test of from 200 to 300 or more 
pounds per square inch, according to the pressure for which the pipe 
is designed, the test pressure being considerably above the actual 
working pressure. While undergoing this test the pipe should be 
sharply rapped from end to end with a hand-hammer to detect any 
weakness. After this test each piece of pipe should be weighed and 
the weight plainly marked thereon in paint. Inasmuch as the pipe 
cannot be cast to exact weight, a maximum allowable variation of 3 to 
4 per cent, from that specified is usually permitted. Lighter weights 
will cause the pipe to be rejected; heavier weights will be allowed, 
but not paid for. 

588. Durability of Cast-iron Pipe.—The life of well-coated cast-iron 
pipe is still to be determined. The question of corrosion is an impor¬ 
tant one, not only with respect to the life of the pipe, but on account 
of the fact that corrosion will greatly reduce its carrying capacity. 
Considerable corrosion may indeed take place on the interior of the 
pipe without greatly impairing its strength. 

The rapidity of the corrosion depends largely upon the character of 
the water, and, generally speaking, those waters containing considera¬ 
ble amounts of free carbonic acid are the worst in this particular. 
Many instances are reported where well-coated pipes appear to be 
practically unchanged after forty or fifty years of use. In other cases, 
especially where the water-supply is soft, some corrosion will take 
place in a few years. At still other places the coating appears to 
have been worn away or to have disintegrated. Usually some corro- 


WROUGHT-IRON AND STEEL PIPE. 5 I I 

sion will take place in ten or fifteen years even with well-coated pipes. 
In most cases the corrosion is much less rapid after it has proceeded 
to a certain extent, and it is probably safe to say that well-coated pipe 
will last at least fifty years, and probably much longer. 

The internal corrosion of pipes occurs in a different way from the 
ordinary rusting of iron. Bunches or knobs, called tubercles, form on 
the surface, which consist for the most part of oxid of iron, with some 
silica, lime, and organic matter. These may increase to a size of 
to 2 inches in diameter, and to i inch thick. At the base of each 
tubercle is usually found a spot where the iron is badly corroded and 
often so soft that it can be cut with a knife. This soft spot may be 
very small, while the coating around may be well preserved. The 
tubercle is supposed to start at a point where the original coating is 
defective, a very small defect being sufficient to allow this to occur. 
The theory of the corrosion is that the iron is attacked by the carbonic 
acid in the water, thus forming ferrous carbonate, which is then oxid- 
zed to ferric hydrate by the oxygen dissolved in the water. The 
carbonic acid is thus set free and is capable of further attacks upon 
the metal. A depression is gradually formed in which the tubercle is 
built up. 

The corrosion of the exterior of a pipe depends largely upon the 
character of the soil. Ashes, cinders, and the like are to be avoided 
for filling. 


WROUGHT-IRON AND STEEL PIPE. 

589. Advantages of Wrought-iron and Steel Pipe.— Wrought iron 
and steel have been used to a considerable extent for water-pipes, and 
for large pipe-lines these materials present considerable advantage 
over cast iron. The question is purely an economical one, and in its 
consideration several factors enter. Since steel is much stronger than 
cast iron, the use of it will give a much lighter pipe, an advantage 
as regards transportation, but a disadvantage as regards durability, 
especially for small sizes. Special forms are not so readily constructed 
of steel, so that for distributing-mains cast iron is much preferable. 
Another disadvantage of steel pipe is that with the ordinary riveted 
joints a considerably larger pipe is required than if a smooth cast-iron 
pipe is used. Thus for a diameter of 42 inches the value of c for a riv¬ 
eted steel pipe may be taken at no (page 236), while for a new cast- 
iron pipe it is about 130. The capacity of the steel pipe is therefore 
only 85 per cent of that of a cast-iron pipe of the same diameter. The 


5 12 


PIPES FOR CONVEYING WA TER. 


discharge being nearly proportional to the necessary size of steel 
pipe to equal the cast-iron pipe in capacity would be given by the pro¬ 
portion whence = 44J- inches, which is about 6 per cent 

larger than the cast-iron pipe. 

Steel pipe is specially adapted to long pipe-lines with few or no 
branches, also for high pressures, and 'for resisting other unusual 
stresses. Several large pipe-lines have been built of steel within the 
last few years, and it may be predicted that the use of this material 
will be greatly extended in the future as better means for its protection 
are devised. Even allowing for its more rapid corrosion, it will prove 
cheaper in many cases to renew it than to invest the additional money 
required for the cast-iron pipe. On the other hand, the inconvenience 
of renewal may be largely against the use of steel. 

Wrought iron has been entirely superseded by steel for riveted 
pipes. Some experiments indicate less corrosion in the case of 
wrought iron, but the difference is not great enough to be worth much 
consideration. 

590. Quality of the Material.—The material used for steel pipes 
should be soft open-hearth steel of a tensile strength of about 60,000 
pounds per square inch, elastic limit one-half of ultimate strength, 
elongation 22 to 25 per cent, and reduction of area 50 per cent. This 
material is about the same as now used in the best stand-pipe construc¬ 
tion. A good quality of material is required to resist the shocks to 
which pipe-lines are often subjected, and to withstand safely the work 
of forging, punching, and calking. 

591. Thickness of Shell.—If = allowable stress per square inch on 
gross section, the required thickness is given by the equation 



where p = total pressure per square inch, including allowance for 

water-hammer, and 
r — radius of pipe in inches. 

The value of ^ depends upon the method of construction. If the 
pipe is a riveted pipe, the longitudinal joints are usually double-riveted, 
and as such have an efficiency of from 60 to 70 per cent. If water- 
hammer is properly taken into account, the safe stress on net area may 
be taken at about 15,000 pounds per square inch, whence the stress on 
gross area will be about 10,000 pounds per square inch, which would 



WROUGHT-IRON AND S7'EEL PIPE. 


513 


be the value of 5 to be used in the preceding equation. For very large 
pipes triple-riveted joints may be employed, in which case the efficiency 
will be about 75 per cent (see also Art. 593). 

In order to equalize somewhat the life of pipes of various sizes, and 
at the same time to prolong it, an allowance of a small amount, such 
as inch, may well be added to the thickness determined from the 
formula. 

592. Joints.—Small sizes of pipe may be made by means of the lap- 
welded joint, or the spirally-riveted joint, or the longitudinal lap-riveted 
joint. Such pipes are made in sections of 1 2 or 15 feet which are con¬ 
nected in the field in various ways, such as by a screw-coupling, or by 
means of a cast-iron bell and a spigot consisting of a steel or wrought- 
iron band, or by riveting, or by merely driving the sections together. 
For large sizes riveted longitudinal and circular joints are usually em¬ 
ployed. Single sheets are bent and riveted to form one section of pipe, 
which may be made either cylindrical in form, or made with a slight 
taper and the sections put together stove-pipe fashion. Lap-joints have 
been commonly used, but this form of joint offers considerable obstruc¬ 
tion to the flow of water, so that in some of the later pipes butt-joints 
have been adopted, and it has been proposed also to employ counter¬ 
sunk rivets. The value of butt-joints and countersunk rivets would be 
proportionally greater the thicker the plates. Whether they would be 
economical would depend on the extra cost involved as compared with 
the saving effected by the reduction in diameter rendered possible. 

In the construction of steel pipes several sections are riveted to¬ 
gether at the shop, usually enough to make a length of 20 to 30 feet. 
These sections are then transported to the field and riveted together 
in place. Special forms of joints, such as described for small pipes, are 
also sometimes used for large pipes, but probably the safest joint for 
the circular seams is the well-calked riveted joint. 

Riveted joints, both in the shop and in the field, should be thor¬ 
oughly calked and tested by water-pressure. 

593. Design of the Riveting. —The design of the riveting follows 
the same general principles as employed elsewhere, and as more fully 
discussed in the chapter on stand-pipe design, Art. 720. The size of 
rivets is usually made about twice the plate thickness up to a maximum 
diameter of about 1 \ inches. The circular joints can usually be made 
strong enough by single riveting, but economy requires the longitudi¬ 
nal joints to be double- or triple-riveted. For any given size of rivet 
the spacing is determined by making the shearing strength of the rivet 
equal to the tensile strength on net section; and this strength divided 


5*4 


PIPES FOR COUPE YING WA TER. 


by the strength on gross section is the efficiency of the joint. The 
•safe shearing strength of rivets may be taken at about 9000 pounds 
per square inch. The rivet-spacing for the East Jersey pipe-line was, 
for example, as follows: 



Inches. Inches. 

Inches. 

Inches. 

Nominal size of pipe. 

...48 

48 

48 

36 

Thickness of sheets. 

... i 

A 

f 

1 

Size of rivets. 

... £ 

i 

3 

8 ' 

£ 

Circular Seams. 

Rivet-pitch... 

... 1.5 

1.8 

2.0 

i-5 

Lap of sheets. 

2 

2f 

, 2f 

2 

Longitudinal Seams (double-riveted). 

Rivet-pitch. 2.277 

2.721 

3125 

2.277 

Distance between rows . . . 

x tV 


T ^ 

1 TV 

x tV 

Lap of sheets. 

• • . 3 

3 i 

4 

3 


In the 72-inch steel pipe at Ogden, Utah, the longitudinal joints 
were double-strap butt-joints, triple-riveted, similar to the joints used 
in marine-boiler practice. The circular joints were double-riveted 
single-strap butt-joints. The calculated efficiency of longitudinal 
joints is from 85 to 87 per cent. The stress on net section varies from 
13,000 to 14,000 pounds per square inch. The pipe was made in 
sections 9 feet 2 inches long, each section consisting of a single plate. 
The field-joints were power-riveted.* 

Steel pipe-lines are usually built without expansion-joints. 
Changes of temperature, therefore, produce certain longitudinal 
stresses which must be considered in designing the circular joints and 
in making connections at valves and other points. The stress per 
square inch on gross section due to temperature changes is given by 
the formula of Art. 577, page 501. For steel, c= about .0000065 
and E = 30,000,000 pounds per square inch. If the pipe is buried, 
the range of temperature will not exceed 40 to 45 degrees, so that, 
assuming the pipe laid at a temperature equal to the maximum, the 
greatest stress caused by a reduction of temperature will be 

s — 45 X .0000065 X 30,000,000 
— 8800 pounds per square inch on gross area. 

Considering the self-adjustments which will take place during the con- 


* Trans. Am. Soc. C. E., 1897, xxxvm. p. 258. 












WROUGHT-IRON AND STEEL PIPE. 5 I 5 

struction of the pipe, the stress caused by temperature changes will 
doubtless be considerably less than that here computed. 

If the pipes are exposed for any great distance, expansion-joints 
become necessary, for the consideration of which reference is made 
to the next chapter. 

594. The Locking-bai' Joint .—A novel form of longitudinal joint 
which appears to have much merit is what is known as the locking- 
bar joint, used recently on some Australian pipe-lines (Fig. 146). In 



Locking- Section of pipe Section of joint-ring, 

bar. near circular joint. 

Fig. 146. —The Locking-bar Joint. 


making this joint the plates are slightly upset at the edges, then in¬ 
serted in the grooves of the bar and the bar pressed down upon the 
plates in an hydraulic press. The pipes are then tested, and if found 
leaky the joints are usually corrected by additional work in the press. 
No calking is required. Tl;is form of joint has proven cheaper than 
the riveted joint, and where it has been used specifications have required 
its efficiency to be as great as that of the plates. Tests by Prof. Unwin 
have shown that this requirement can be readily met. This joint pos¬ 
sesses a very considerable advantage over the riveted joint in that it 
forms no obstruction to the flow of water beyond causing a slight reduc¬ 
tion in the cross-section of the pipe. The figure also illustrates the 
joint-rings for the circular joints. These joints are made with lead 
as for cast-iron pipes.* 

595. Special Details.—Changes in direction are usually made by 
forming one or more joints at a small bevel. Two or three standard 
bevels of small angle may be adopted, and any desired curve made by 
the use of one or more of these bevels. Branches, etc., for the 
ordinary sizes of pipes, are usually made of cast iron and are riveted 
or bolted firmly to the steel pipe. Valves are joined to the pipe in 
a similar manner by means of cast-iron flanges. In connecting large 
mains Mr. Herschel has adopted the plan of using several small cast- 
iron flanged connections, an arrangement which allows the use of small 
castings and small valves. Riveted specials are sometimes used for 
large pipes. 

596. Coating of Steel Pipe.—The tar coating employed for cast-iron 
pipe is not so successful when applied to steel or wrought iron, but the 


* Eng. News, 1898, xxxix. p. 373; XL. p. 423. Eng. Record, 1900, xli. p. 178. 












5!6 


PIPES FOR CONVEYING WATER. 


necessity of a perfect coating is even greater in this case on account 
of the comparative thinness of the metal. Some form of asphalt coat" 
ing has usually been employed. The ordinary method of applying 
the coating is to dip the pipe .in liquid refined asphalt heated to a tem¬ 
perature of 280 to 350 degrees, as in the coal-tar process. A second 
dipping to thicken the coat is often used. Various mixtures of asphalt 
and tar have been tried, but with no better results than with the pure 
asphalt. 

A process of applying asphalt varnish, known as the Sabin process, 
has been used in some recently constructed pipe-lines with apparently 
more success than has accompanied the old method. In this process, 
the pipe, after dipping, is baked for several hours at a temperature of 
400 to 600 degrees, thus producing an enamel coating. 

In all cases the pipe must be thoroughly cleaned before coating. 
The specifications for the Coolgardie pipe-line require the pipe to be 
cleaned by being dipped, first in dilute sulfuric acid, and then in a bath 
of lime-water. The coating consists of Trinidad asphalt and creosote. 
The coating of the Bundalier pipe-line is composed of equal parts of 
asphalt and coal-tar. 

Still another form of coating recently used is known as “mineral 
rubber ” asphalt. It is composed of asphalt, but the process is secret. 
The pipe is dipped but not baked. This process was adopted at Min¬ 
neapolis in 1897, and has been used in several other important works. 
The results so far appear to be quite promising. 

In transportation and in construction in the field great care must 
be exercised to avoid injuring the coating. Some protective covering 
of pieces of old carpet or canvas should be used, and the workmen 
required to wear rubber shoes. The field-joints and all places where 
the coating has been injured should be coated by applying with a 
brush some kind of protective paint. Asphalt dissolved in carbon 
bisulfide (P. & B. paint) is often used, but the fumes from it are very 
objectionable to the workmen. Various other asphalt paints or var¬ 
nishes are also used for this purpose. 

597. Durability of Steel Pipe. —Steel pipe coated with asphalt has 
in some cases been reported to be in perfect condition after a lapse 
of thirty or forty years. In other cases corrosion has been quite rapid, 
so that the life of the pipe has been short as compared to that of cast iron. 
The Rochester wrought-iron pipe built in 1873-5 has in twenty-one 
years required a little repairing by means of patches placed on the out¬ 
side. During this time eight plates out of a total of 14,000 have been 
thus repaired. No leaks have developed at riveted joints. The Roches- 


WOODEN PIPE. 


5 17 


ter pipe was coated with Trinidad asphalt and coal-tar. Mr. Freeman 
in estimating the cost of steel pipe-lines for New York City assumes 
their life at fifty years, but provides for their cleaning and painting 
about every ten years.* 


WOODEN PIPE. 

598. Advantages of Wooden Pipe—It was noted in the introduction 
that the use of wood for water-mains was quite universal in the early 
days of water-works construction, and that this material was subse¬ 
quently displaced by cast iron. The use of wooden pipe under certain 
conditions has now again reached considerable proportions in certain 
parts of the country. 

In general, wooden pipe is practically adapted to those locations 
where transportation of iron is very expensive and where wood is 
relatively cheap. When properly constructed, wooden pipe is very 
durable; it is not subject to corrosion by electrolysis nor affected by 
changes of temperature, and it also furnishes good protection to the 
water against cold and heat in exposed locations. It possesses an¬ 
other very considerable advantage in the smoothness of the interior 
and in the fact that the capacity does not become reduced through cor¬ 
rosion. The special field for wooden pipe is for low pressures and 
moderate sizes, where a metal pipe, if used, would necessarily have 
excessive strength. 

599. Bored Pipe.—The manufacture of bored pipe for water-mains 
has been somewhat revived in recent years, and a considerable amount 
of such pipe is now manufactured under the name of “improved 
Wyckoff pipe.” The pipe is made from solid logs, but it depends for 
strength upon spiral bands of flat iron which are wound tightly about 
it from end to end. The exterior of the pipe is coated with pitch as a 
protection to the bands. The joints are made by means of wooden 
thimbles fitting tightly in mortises in the ends of the pipe, and, in lay¬ 
ing, the sections are driven together by means of a wooden ram. 
The interior surface is smooth and continuous. The pipe is made in 
sections 8 feet long, and in sizes from 2 to 17 inches in diameter. 
The bands are spaced according to the pressure. Branch connections 
are made by means of cast-iron specials which have long sockets into 
which the wooden pipe is driven. About 1500 miles of this pipe is 
reported to be now in use. It is very durable and is said to cost some- 


* Report on New York’s Water-supply, 1900, p. 320. 




PIPES FOR CONVEYING WATER. 


518 

what less than cast iron where the transportation charges are not 
excessive. 

600. Stave-pipe.—The necessities of water-carriage in the West, 

and the expense of iron pipe in that region, have developed a very 
efficient form of wooden-stave pipe. As early as 1874 Mr. J. T. 
Fanning built such a pipe at Manchester, N. H., which is still in use,; 
but the chief development of this type of construction has taken place) 
in the West since 1883, at which time stave-pipe was first extensively/ 
used at Denver. ■ 

The pipe is built continuously in the trench. The staves are, 
formed with radial edges, and are bound tightly together by means of 
round or oval bands of steel or iron, spaced and sized according to 
the pressure, and fastened by shoes and nuts. The general form ol 
construction and method of building will be clearly understood by ref¬ 
erence to Figs. 147 and 148. The latter illustration shows also the 
method of carrying a wooden pipe across a narrow gorge. '■ 

Two types of stave-pipe have been employed. In one of these, 
the Allen patent, the outside and inside surfaces of the staves are made 
concentric. The staves are made to break joints, and the end joint? 
are made tight by inserting small steel plates in saw-kerfs in the staves. 
In the other form, the Durelle patent, polygonal staves 16 to 20 feei 
long are used which have a slight tongue and groove formed on tha 
edges. The staves do not break joints, but the end joint is made by 
surrounding the pipe by a layer of staves 4 feet long. The former 
type has been most frequently used. 

Stave-pipe is suited to pressures up to about 100 pounds per squar 
inch. Above this limit it will usually be less economical than steeT 
as the bands become very heavy and numerous. Stave-pipe has been 
constructed in sizes from 1 foot up to 9 feet in diameter.* 

601, General Requirements for Staves and Bands.—The staves 
should be made of clear stuff and be somewhat seasoned. California 
redwood and Oregon fir have been most frequently employed. The 
staves should be thick enough to prevent percolation and not deflect 
appreciably between bands. In practice the size varies from about 1 
inch by 4 inches to 2^ by 8 inches. 

Bands should be made of a good quality of soft steel, and should be 
upset for the sake of economy. They should be thoroughly coated 
with asphalt before being used. They must be of such a size and so 
spaced as to withstand the stresses to which they are subjected, prevent 

* For a full and valuable discussion of the design and construction of stave-pipe 
see paper by A. L. Adams in Trans. Am. Soc. C. E., 1899, xli. p. 27. 



























































































































































Fig. 148. —Stave-pipe, Santa Ana Canal. 

(From Trans. Am. Soc. C. E., vol. xxxm.) 



Ul 

to 











WOODEN ' PIPE. 


523 


flexure of the staves sufficient to cause leakage, and not injuriously crush 
the fibers of the wood. To resist the water-pressure large bands and 
wide spacing will in general be most economical, but the size is lim¬ 
ited by the requirement that the band must not crush the wood when 
fully stressed, and the spacing must not exceed a certain maximum. 

In practice the thickness of staves to give durability and prevent 
percolation will allow a maximum spacing of 10 to 12 inches under 
light pressures. Under any considerable pressure, other requirements 
will govern the size of bands and the spacing. • 

602. Size of Bands.—As the size of a band increases, its strength 
increases as the square of the diameter, while the safe pressure upon 
the wood increases only as the first power of the diameter, so that for 
each case a definite limit exists for the size of band which may be 
used. Experience shows that the width of contact of round bands with 
the wood, when the latter is compressed within safe limits, is about 
equal to the radius of the band. The ultimate crushing strength of the 
wood is from 1000 to 2000 pounds per square inch, and the safe stress 
is usually taken at from 600 to 750 pounds. Mr. Adams, in the paper 
referred to on page 518, uses a value of 650. Adopting this figure 
and letting r — radius of band, and e = safe pressure per lineal inch 
of band, we have e = 650^. Further, let .S' = safe strength of band, 
R = internal radius of pipe, and t — thickness of pipe; then 

5 = (R -f- t)e = ( 7 ? + t) 6 $or, .(5) 

from which equation the size of band is determined. A factor of safety 
of about 4 is usually employed. 

In case the calculated size of band will, by the formula for spacing 
given in the next article, correspond to a spacing greater than 10 or 
12 inches, then the spacing should be assumed at the maximum allow¬ 
able value and the size of band calculated by eq. (6). This will occur 
for li or ht pressures only. Bands less than f inch should not be used. 

From these considerations Mr. Adams has made up a table, repro¬ 
duced in Table No. 76, which gives a suitable size of stave and the 
maximum size of band for different diameters of pipe, using a factor of 
safety of about 4 for the bands. Oval bands are assumed for pipes 
20 inches in diameter or less, in order to secure a greater proportionate 
area of contact. For the 10-, 12-, 22-, and 30-inch pipes the bands 
used cannot be stressed to their full working value without crushing 
the wood. The permissible working stress given is such as will give 

a value of e equal to 650^. 


5 2 4 


PIPES FOR CONVEYING WATER. 


603. Spacing of Bands.—The size being determined, the spacing 
will depend upon the stresses. These are from three sources: 

1. The initial tension. 

2. The stress due to water-pressure. 

3. The stress due to the swelling of the wood. 

TABLE NO. 76 . 


ECONOMIC PROPORTIONS FOR STAVE-PIPE DESIGN (ADAMS). 


Nominal 
Diameter 
of Pipe. 

Stock Sizes 
Staves. 

for 

Thickness of 
Finished 
Staves. 

Economic Sizes 
of Bands. 

Working Stress 
in Band. 

S'. 

Factor of Safety 
in Band. 

Inches. 





Pounds. 








Oval. 




10 


X 

4" 

ItV" 

5 " v 7 " 

T¥ * TS 

1255 

5-26 


12 


X 

4 


5 N/ 7 

TIT * T¥ 

1475 

4-47 


14 


X 

4 

T ® 

1 T¥ 

5 V 7 

T¥ A T?r 

1650 

4 


16 

2 

X 

6 

T 7 

*¥¥ 

5 V 7 

T¥ A IS 

1650 

4 


18 

2 

X 

6 

T 8 

5 v 7 

T¥ X Tg 

1650 

4 


20 

2 

X 

6 

T ^ 

5 V 7 

T¥ A t¥ 

Circular. 

1650 

4 


22 

2 

X 

6 

T 3 

x ¥ 

3 

8 

1503 

4.4 


24 

2 

X 

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If, after a pipe is filled with water, the bands be loosened until the 
wakr begins to percolate through the cracks, the stress will then be 
due to (2) only, but this condition is impracticable of attainment. In 
actual practice the staves are more or less seasoned and the bands 
screwed up tightly at first. The wood will readily swell 2 or 3 per 
cent, which is an amount far beyond the capacity of the bands to allow 
by virtue of their elasticity and their sinking into the wood; so that 
the total force on the bands is approximately equal to the swelling- 
power of the wood (crushing-strength of saturated wood) plus the water- 
pressure. The swelling-power of the staves appears, from experiments 
by Mr. A. C. HennyA to vary from 50 to 200 pounds or more per 
square inch,—ordinarily from 75 to 150 pounds. Adams assumes 100 
pounds, and this is probably a sufficiently high value. 

To determine the spacing we have then, if d = spacing of bands in 


* Trans. Am. Soc. C. E., 1899, vol. xli. p. 76, 






















WOODEN PIPE. 


525 


inches, p = water-pressure per square inch, and e' — swelling-force of 
wood per square inch, with other notation as on page 523, 

5 = pdR e'td, 


whence 


d = 


S _ S 

pR -|- e't ~~ pR 100/’ 



In this formula, 5 is the safe strength of the band as determined 
by the application of eq. (5). 1 he size of the band and its working 

stress may also be taken from Table No. 76. If the spacing as found 
from eq. (6) is greater than the maximum allowable, then d should be 
assumed, the value of 5 computed, and the size of band selected 
accordingly. 

For large sizes and high pressures the term e't is relatively small 
and a formula for spacing based on water-pressure alone, namely, 


d — is sufficiently accurate, and is used by some engineers. For 

small sizes and low pressures it is desirable, however, to take account 
of the swelling action. 

It is to be noted that no account has been taken of initial tension. 
It has, however, been assumed that the stress on the band is caused 
by full water-pressure plus the swelling-power of the staves, and this 
is the maximum force which can act upon the bands. 

604. Coupling-shoes.—The coupling of the bands is made by means 
of a malleable-iron or steel shoe closely fitting the pipe, and of a strength 
equal to that of the bands. The design of this shoe is a matter of con¬ 
siderable importance and some difficulty. It should be so made as to 
strain the bands axially, it should have a good bearing on the staves 
so as not to cause undue pressure, and it should be convenient and 
made as light as possible, consistent with strength. Two forms of 
shoes are illustrated in Fig. 149. The first is of malleable cast iron, 
while the second is a forged shoe. The first requires a forged head 
on the band, and the second a loop-eye. The pressure between shoe 
and pipe is quite uniform in both these forms, which is not true of 
some that have been used. Other forms are illustrated in Mr. Adams’s 
paper. 

605. Specials.—Stave-pipe can readily be built to a curvature of 
from 200 to 300 feet radius by springing the staves into place. Con¬ 
nections are usually made by means of castings with deep bells, into 
which the pipe is built and calked with oakum and paint. Variations 
in diameter are made by the use of tapered staves. Repairs can very 
readily be made in this kind of pipe. 




526 


PIPES FOR CONVEYING WATER. 


606. Leakage and Durability of Wooden Pipe.—Tests of pipe-lines 

have shown in some cases practically no leakage. In others, a slight 
leakage has been observed which, including evaporation from the 



Fig. 149. —Coupling-shoes for Wood-stave Pipe. 

(From Trans. Am. Soc. C. E., vol. xli.) 


surface, has amounted to from .053 to .086 gallon per square foot per 
day. Mr. Henny considers that a leakage of .05 gallon per square 
foot per day is a safe allowance for exposed pipes. 

The durability of wooden pipe is chiefly a question of the life of 
the bands. Wood, itself, when kept saturated with water has an 
almost indefinite life, old water-mains in Philadelphia, New York, and 




















































VARIOUS MATERIALS EMPLOYED FOR WATER-PIPE. S 2 7 


Boston having been found perfectly sound after sixty or seventy years 
of use. The bands are of a form favorable to resist corrosion. They 
will doubtless last longer if the pipe is not covered, but the contrary is 
probably true of the wood. To preserve the wood it is essential that 
the pipe remain always full of water. Most of the wooden stave-pipe 
is of comparatively recent construction, but there are instances where 
pipe of this kind has been in use for more than forty years and is still 
in good condition. It is probably true that its life is about as great 
as good steel pipe, and considerably greater than thin steel pipe which 
would ordinarily be used in its place. 

OTHER MATERIALS EMPLOYED FOR WATER-PIPE. 

607. Cement Pipe.—Pipe made by lining a core of wrought iron 
inside and out with cement mortar has been much used in the eastern 
part of the United States, but is now employed in very few places. 
It is still reported to give satisfactory service in some cases, but it has 
generally been abandoned for cast iron. There is great difficulty in 
maintaining the cement coating intact, and if it is broken the iron core 
soon corrodes. Its life is in many places not over ten years. 

For large conduits some form of construction employing a com¬ 
bination of steel and concrete would seem to possess much merit. In 
such conduits the steel could be covered in place and the thickness of 
the concrete made sufficient to give good protection. At Paris a large 
sewage-conduit has been constructed after this manner. A thin steel 
core is used, around and inside of which is placed a network of rods 
to furnish the necessary strength. All is then encased with concrete.* 

608. Vitrified-clay Pipe has been employed in a few places for con¬ 
duits. It is cheap, indestructible, and when the joints are carefully 
made the leakage is very small. It is generally used under no pres¬ 
sure, but in one or two instances has been designed to carry considera¬ 
ble pressures. Vitrified pipe has recently been recommended, in a 
report to the city of Oakland, for salt-water mains to furnish water for 
street-sprinkling.t It was thought it could easily be made to with¬ 
stand 100 pounds pressure. The form of joint was to be of strips of 
burlap dipped in asphalt, which form has been well tested under 40 to 
50 pounds pressure. At Florence, Colorado, a 7-mile conduit of 12-inch 
vitrified pipe has been built. It is not under pressure. Vitrified pipe 
has also been extensively used at Little Falls and at Amsterdam, N. Y., 

* Annales des Ponts et Chaussees, 1897, II. p. 1; Eng. News, 1898, xxxix. p. 170. 
f Eng. News , 1899, XLil. p. 149. 




528 


PIPES FOR CONVEYING WATER. 


a length of 5.63 miles having been constructed at the former place. 

A very considerable saving was thus secured. Deep sockets were used 
and the joints carefully made by means of jute soaked in Portland 
cement, with which material the joint was thoroughly filled to within 
1 inch of the outside. The remainder of the space was filled with 
Portland-cement mortar. The cost of the Little Falls conduit of 12- 
to 20-inch pipe was about $ 1.50 per foot, which was about one-half 
the cost of cast-iron pipe. 

609. Materials for Service-pipes.—Service-pipes, or pipes for con- . 
ducting water to individual consumers, are made of a considerable 
variety of materials. Uncoated iron pipe, or pipe coated only with 
tar, is not serviceable for such small sizes (usually j- to ij inches in 
diameter), as even a small amount of tuberculation would completely 
clog up the pipe. Galvanized, tin-lined, lead-lined, and cement-lined 
iron pipe are widely used, but the most common, is lead pipe. Lead 
pipe is practically indestructible, but rather expensive and heavy for 
high pressures. In some places it cannot be used with safety on 
account of the danger of lead poisoning. Certain waters only will 
attack lead to a sufficient extent to render its use dangerous, but, de¬ 
spite the study that has been put upon the subject, it is not yet fully 
known, without actual experiment, what effect various classes of waters 
will have. 

Recently the Massachusetts Board of Health has investigated this 
question by reason of several cases of lead-poisoning that have occurred 
in that State.* Thirty cases were especially studied in which lead 
pipe was largely used: In general it was found that waters having 
the greatest amount of dissolved solids and hardness dissolve the least 
amount of lead, and that the active agents causing the solution of the 
lead are oxygen and carbonic acid. The latter is characteristic of soft 
waters. In fifteen towns with ground-water supplies the average 
amount of lead ranged from .0055 to .1899 part per 100,000 with 
pipes in ordinary use, and from .0108 to 8.38 parts when the water 
had stood in the pipes. Surface-waters in fourteen towns averaged 
similarly from .0031 to .0788, and from .0099 to .3921 parts respec¬ 
tively. In four cities with ground-water supplies, cases of lead-poison¬ 
ing were prevalent, and in these four cases the lead averaged o. 2 part, 
after the water had stood several hours in the pipes. No cases of 
poisoning occurred with surface supplies. Experiments on galvanized 
iron and plain iron showed more action than on lead, but with tin the 
corrosion was very little. 


* Report for 1898, p. 539. 





LI TER A TURE. 


529 


As to the amount of lead which will give trouble it is known that 
continuous use of water containing .05 part per 100,000 has caused 
serious injury to the health. Zinc is not dangerous in the amounts 
likely to be present. Galvanized pipe is not, however, very durable. 

Cement-lined pipe is quite largely used in the East, but in many 
places it does not prove to be very durable for the same reason as 
given in Art. 607. It has, however, given good service in some 
cities. 

Tin-lined pipe is now being used to a considerable extent. It is 
quite expensive, but the experience with it so far indicates that it may 
be very durable. 


LITERATURE. 

(See also references of Chapter XXV.) 

CAST-IRON PIPE. 

1. Jamieson. The Internal Corrosion of Cast-iron Pipe. Proc. Inst. C. E., 

1880-81, lxv. p. 323. 

2. Howland. Water Pipes. Proc. Eng. Club Philadelphia, 1886, vi. p. 55. 

3. Russell. Thickness of Water-pipe. Jour. Assn. Eng. Soc., 1889, vm. 

p. 100. 

4. Cement-joints for Cast-iron Water-mains. Eng. News, 1892, xxvm. 

p. 2 35 * 

5. Brackett. Uniformity in Designs for Special Castings. Jour. New Eng. 

W. W. Assn., 1893, vm. p. 78; Eng. News, 1893, xxix. p. 579. 

6. Duane. The Effect of Tuberculation on the Delivery of a 48-inch Water- 

main. Trans. Am. Soc. C. E., 1893, xxvm. p. 26. Valuable dis¬ 
cussion. 

7. Life of Cast-iron Water-pipe at St. John, N. B. Eng. News, 1894, xxxi. 

p. 15. Experience with wooden joints. 

8. Lewis. Cast-iron Water-pipe. Gassier s Mag., 1895, vm. p. 17. 

9. Garrett. Making Cast-iron Pipe. Jour. New Eng. W. W. Assn., 1896, 

xi. p. 27. 

10. Coating of Cast-iron and Steel Riveted Pipe. Report of Com. of Am. 

Soc. of Munic. Imp., Mnn. Eng., 1897, xm. p. 280. 

11. A 61-inch Cast-iron Pipe-line. Eng. Record, 1898, xxxvn. p. 51. 

12. Wiggin. The Manufacture and Inspection of Cast-iron Pipe. Jour. 

Assn. Eng. Soc., 1899, xxii. p. 209. 

13. Brackett. Water-pipe on the Metropolitan Water-works. Jour. New 

Eng. W. W. Assn., 1899, xm. p. 3 2 5 - 

14. Murdoch. Wooden Joints in Cast-iron Water-mains. Jour. New Eng. 

W. W. Assn., 1900, xv. p. 34. 

(For references to methods of removing incrustation, see Literature of 
Chapter XXIX.) 


530 


PIPES FOR CONVEYIAG WATER. 



STEEL PIPE. 

1. de Varona. Report on the Use of Cast Iron, Wrought Iron, and Steel 

(for the Brooklyn Conduit). Proc. Am. W. W. Assn,, 1894, p. 181. 

2. The Specifications for Riveted Steel Pipe, Cambridge, Mass. Eng. 

Record , 1895, xxxi. p. 97. 

3. The Specifications for the New Bedford Force Main. Eng. Record , 1896, 

xxxiii. p. 293. 

4. Cast-iron vs. Steel Pipe. Eng. Record , 1896, xxxiii. p. 349. Compari¬ 

son of cost. 

5. Clarke. The Distortion of Riveted Pipe by Backfilling. Trans. Am. 

Soc. C. E., 1897, xxxviii. p. 93, 

6. Kuichling. The Joints of Riveted Water-pipe. Lecture at Rensselaer 

Poly. Inst. Eng. Record, 1899, xl. p. 33. 

7. Hastings. Use of Steel for Water-mains. Jour. New Eng. W. W. 

Assn., 1899, xiii. p. 314. 

8. Sabin. Experiments on the Protection of Steel and Aluminum Exposed 

to Water, Trans. Am. Soc. C. E., 1900, xliii. p. 444. 

9. Asphalt Coatings for Water-pipe. Eng. Neivs, 1900, xliii. p. 331. 

10. Freeman. Construction, Cost, and Water-carrying Capacity of Large 
Steel Conduits. Report on New York’s Water-supply, 1900, p. 320. 

WOODEN PIPE. 

1. Fanning. A Water-conduit under Pressure. Trans. Am. Soc. C. E., - 

1876, vi. p. 69. Description of the Manchester wood-stave pipe. 

2. Henny. Wooden-stave Pipe vs. Riveted Pipe. Jour. Assn. Eng. Soc., 

1898, xxi. p. 239. 

3. Wyckoff Pipe used in the Water-works of North Tonawanda. Eng* 

Record, 1898, xxxviii. p. 515. 

4. Wells. Improved Wyckoff Pipe. Jour. New Eng. W. W. Assn., 1899,, 

xiii. p. 288. 

5. Adams. Stave Pipe: Its Economic Design and the Economy of its Use. 

Trans. Am. Soc. C. E., 1899, xli. p. 27. 

6. Henny. Nine-foot Wood-stave Pipe, Floriston Pulp and Paper Co.,. 

Floriston, Cal. Eng. News, 1900, xliv. p. 235. 

VITRIFIED CLAY PIPE. 

1. Babcock. The Use of Salt-glazed Vitrified Pipe in Water-works Con¬ 

struction. Eng. Record, 1888, xvn. p. 361. 

2. Notes on Vitrified-pipe Conduit at Little Falls, N. Y. Eng. News, 1895, 

xxxiv. p. 283. 

3. Maury. Tests of the Tightness of a Vitrified Earthenware Water-conduit. 

Eng. News, 1896, xxxv. p. 341. 

4. Miller. Report on Proposed Salt-water Street-sprinkling Plant at Oak¬ 

land, Cal. Eng. News, 1899, xlii. p. 149. Relates to the use of 
vitrified pipe. 

5. Tests of Asphalt Joints of Vitrified Pipe. Eng. Record, 1899, xl. p. 94. 

6. Garrett. Florence, Col., Water-works. Eng. Record, 1900, xli, p. 147. 

Describes use of vitrified pipe. 


I 





LITER A 1 URE. 


531 


SERVICE-PIPES. 

1. Service-pipes. Jour. New Eng. W. W. Assn., 1891, p. 22. A discussion. 

2. Chace, Service-pipes, Defects and the Remedy. Jour. New Eng. W. W. 

Assn., 1897, xii. p. 41. 

3. Clark. The Action of Water upon Lead, Tin, and Zinc. Report Mass. 

Board of Health, 1898, p. 541. 

4. Forbes. Cement-lined Service-pipes. Jour. New Eng. W. W. Assn., 

1900, xv. p. 44. 


CHAPTER XXV. 




CONDUITS AND PIPE-LINES. 

610. Where the source of supply is at a considerable distance from 
the place of consumption the design and construction of the necessary 
works for conducting the water is a matter of great importance and 
demands special consideration. Usually a distant source is at a higher 
elevation than the city to be served, so that it will be possible to con¬ 
vey the water partly or wholly by gravity. In many cases, however, a 
part or the whole of the water will require pumping, so that the design 
will also involve a study of possible pumping arrangements. It will 
usually be necessary to consider several designs based upon different 
locations and often upon different types of conduits. In determining 
upon the dimensions of a large conduit the utmost care should be taken 
in selecting the coefficient to be used in the hydraulic formulas em¬ 
ployed. 

611. Classes of Conduits, —Conduits are divided into two general 
classes: (i) those in which the water-surface is free and the conduit 
therefore not under pressure, and (2) those flowing under pressure. 
To the first class belong open canals, flumes, aqueducts, and usually 
tunnels, and to the latter belong pipe-lines of iron, steel, wood, or 
other material capable of resisting hydraulic pressure, and sometimes 
tunnels. Conduits of the first class must obviously be constructed 
with a slope equal to that designed for the water-surface, or equal to 
the hydraulic gradient. This will be a very light and uniform slope, 
and such conduits will therefore often require in their construction long 
detours to avoid hills and valleys, or resort must be had to high bridges, 

■ embankments, cuttings, or tunnels. Conduits of the second class may 
be constructed at any elevation below the hydraulic grade-line, but if 
built above they must be arranged to act as siphons. The selection 
i of the form of conduit is principally a question of economy, and in 
this respect topography will largely govern, but consideration will also 


532 





CA PA Cl T Y—L 0 CA TION. 


533 


be given to various advantages, such as are mentioned in the following 
discussion. 

612. Capacity of Conduits. —Where the conduit is long, sufficient 
storage capacity is usually provided in the vicinity of the city to 
equalize the demand over several days or weeks, so that the capacity 
of the conduit may be based on the average monthly or seasonal con¬ 
sumption. The extent to which provision should be made for the. 
future depends much upon the type of conduit. The question must be 
settled in accordance with the principles laid down in Chapter XI. In 
the case of a masonry conduit the expense of additional capacity is- 
relatively small, so that it will be economical to provide for a long 
period in the future, such as thirty or forty years. Very often the: 
capacity should be made equal to that of the watershed drawn upon.. 
In the case of pipe conduits a much less liberal provision should be 
made for the future, as the expense of additional capacity is propor¬ 
tionately much greater. 

613. Single or Double Conduits. —Security against the interruption 
of the supply demands either that there be two conduits, or that there 
be sufficient storage capacity at the city end to allow the shutting off 
of the supply to permit of any repairs which may be needed. The 
latter method will usually be the cheaper except for very short lines. 
The storage capacity necessary to allow of repairs will vary from three 
to four days’ consumption in the case of small pipe-lines easy to repair, 
up to ten or fifteen days’ supply for large aqueducts. The amount of 
storage considered necessary for this contingency should never be 
drawn upon for other purposes. If a pressure conduit is used and a 
double line is considered the most economical, or if the second line is 
built subsequently to provide added capacity, the two lines should be 
connected at frequent intervals. A section of either can then be shut 
off and the supply carried for a short distance in one pipe, which will 
result in but a small increase in the total head consumed or a small 
decrease in total flow. Where a single conduit is deemed most 
economical for the greater portion, it may still be advisable to build a 
double line at certain points where a breakage would be a very serious 
matter, as at river crossings, etc. 

614. Location of Conduits — The location .of a conduit is a matter 
requiring much skill and judgment. It involves the question of avail¬ 
able slope or hydraulic gradient, cost of conduits of different forms and 
sizes and built of different materials, and frequently the cost of pump¬ 
ing. In the matter of slope there may be sufficient to enable the 


I 


'534 CONDUITS AND PIPE-LINES. 

water to be conducted entirely by gravity, or pumping may be required 
at one or more points. 

In the case of conduits not under pressure, if the total head is 
closely limited, then the slope must be maintained nearly uniform 
and a location found, if possible, which will support the aqueduct at 
the desired elevation. A proper balance must be obtained between a 
circuitous route avoiding high crossings, and a more direct route which 
is more expensive per mile. Usually two or more possible routes will 
need to be examined in detail and comparative estimates made. If 
the available head is large, then a more economical location can prob¬ 
ably be made, as the slope can be varied to a considerable extent, in 
order to best fit the ground, and can also be made steep so as to give 
small sizes. If the country falls more rapidly than is permissible for 
the conduit, then the water may be let down at intervals in special forms 
of construction designed for the purpose. 

The location of pressure conduits is comparatively simple. For them 
a more direct line can be adopted, but at the same time low pressures 
are to be desired. There should be as few summits and depressions 
as practicable, and small sags should be avoided. To provide oppor¬ 
tunity for easy regulation of the pressure it is desirable that the conduit 
approach close to the hydraulic grade-line at occasional intervals, as 
more fully explained in Art. 629. 

Tunnels may be constructed at the grade-line and hence flow free, 
or they may be built at a lower elevation and flow under pressure. 
Usually the former will give the shorter and cheaper tunnel, but in 
some cases it is expedient to build tunnels at a greater depth, as in the 
Croton aqueduct, where 7 miles of tunnel is under a pressure of about 
55 pounds, the chief purpose being to avoid interference with valuable 
property. 

Long conduits usually include both masonary aqueducts and pipe¬ 
lines, each class being used where most suitable. The former is used 
as a rule where the ground lies near or above the hydraulic grade-line, 
and the latter where it lies below for any considerable distance. High 
- and long aqueduct bridges are no longer built, a pressure conduit 
being substituted, which may follow the ground-profile closely. How¬ 
ever, as the transition from open to pressure conduits involves some 
additional details, it will often be cheaper to support the former on 
bridges where the height is but moderate. Where pumping is required 
the expense of raising water must be considered in fixing upon the size 
and slope of the conduit. In the case of a pipe conduit the slope or 
head consumed involves only the question of size, and the proper size 


CANALS. 


535 


to make the total cost a minimum can be quite easily determined, as 
shown in Art. 632. With an open conduit, however, the topography 
will very largely determine the slope and therefore the size. 

The proper location of a conduit requires full and careful surveys, 
including numerous borings and test-pits to determine the character of 
the material. The maps of the United States and various State geo¬ 
logical surveys are of the utmost help in this connection. 

CANALS. 

615. Use of Canals. —The open canal is not often used for conveying 
water for city use, but for irrigation purposes it is the common form of 
conduit. For the former purpose it has several objections, such as 
loss of water by percolation and evaporation, exposure of water to 
pollution from surface drainage and otherwise, and exposure to summer 
heat, which not only warms the water but promotes vegetable growth. 
In irrigation-canals the seepage often amounts to 1 or 2 vertical leet 
per day, an amount which would scarcely be permissible in a city 
water-works conduit, where a large expense has been put upon storage- 
reservoirs, and, as is often the case, where the total capacity of the 
watershed is nearly reached. However, where a canal can be con¬ 
structed with little cutting or embankment, and where the material is 
nearly impervious, it may be the best form of construction. 

If the material is porous, it would probably be better to adopt the 
covered masonry conduit than to incur a large expense in constructing 
a puddle or concrete lining to a canal. A very favorable location for 
an open canal is where a stream-bed can be made into a canal to carry 
water from one reservoir to another lower down the valley. In this 
case there will usually be no loss by seepage,but rather a gain by infil¬ 
tration of ground-water. In side-hill work, or in country of any diffi¬ 
culty, the masonry aqueduct will likely be the cheaper form of con¬ 
struction. For very large quantities of water .the economy of canals 
will be more pronounced. In considering the adoption of a canal the 
possible pollution of the water should be carefully considered. 

616. Slopes and Velocities. —If the available head permits, the most 
economical slope will be such as will give the maximum permissible 
velocity for the material and therefore the minimum cross-section. 
Topography may require the use of a much less slope than this, but 
a greater slope cannot be used without danger of erosion, or an in¬ 
creased cost in protection by paving or otherwise. If the slope of the 
ground is too great, then the fall may be concentrated at certain points 


536 


CONDUITS AND PIPE-LINES • 


where special precautions are taken. With a small available head the 
velocity will be low and the section will have to be made large to cor¬ 
respond with the low velocity. 

The allowable velocities for unprotected canals vary from about i£ 
to 2 feet average velocity for light sandy soils, 2 \ to 3 feet for ordinary 
firm soils, and 3 to 4 feet for hard clay and gravel. In rock or hard- 
pan 5 to 6 feet may be allowed. A velocity of 2 to 3 feet per second 
is sufficient to prevent silt deposits and the growth of weeds. 

The velocity and discharge for any given slope and cross-section is 
calculated from Kutter’s formula. In using this formula the selection 
of a proper value of n is a matter of much uncertainty. For unlined 
channels it is usually taken at .020 to .025 (see Chapter XII). If 
vegetation is allowed to accumulate in the canal, a large allowance 
must be made for increased resistance caused thereby. 

617. Cross-sections. —The cross-section of a canal is usually trape¬ 
zoidal in form. For any given side slope the trapezoidal form giving 
the greatest hydraulic radius, and hence the most economical form as 
regards slope, is one in which the sides and bottom are tangent to a 
circle whose center is at the water-surface. The hydraulic mean 
radius of such a section is one-half the depth of the water. The side 
slope giving a maximum value for the radius is 60 degrees with the 
horizontal, and the water-section would be one-half a regular hexagon, 
but such a section could not be constructed except in very stable 
ground. For a rectangular section, or one with vertical walls, the 
width should be twice the height. The hydraulic radius of the rectan¬ 
gular section is 0.355 ^and of the semihexagonal section is .38 \ f A y 
where A is the area of cross-section. The section having the least 
water-surface is the triangle, and the best slope of the sides is 45 
degrees. 

The sections above described will give a minimum of excavation, 
but are suitable only for small canals. For large canals the material 
will be more economically handled if the section is made somewhat 
wider and shallower. Furthermore, if the canal is made partly by 
excavation and partly by embankment, and if the excavated material 
is suitable for embankment construction, the amount of excavation will 
decrease as the width of channel increases. Too wide and shallow a 
channel is, however, not desirable, as the velocity will be diminished, 
vegetable growth will be more troublesome, and the reduction of sec¬ 
tion due to ice will be proportionately greater. Very large canals are 
sometimes made ten to fifteen times as wide as deep. In side-hill 
Work the amount of excavation will increase with increase in width 


CANALS. 


53? 


beyond a certain point. Too deep a channel will also be unsuitable in 
such situations. Fig. 150 illustrates a section built almost entirely by 



Fig. 150.—Canal Section in Embankment. 


embankment. The best material is placed in the center of the embank¬ 
ments, and drainage-ditches for surface-water 
are provided. Fig. 151 illustrates suitable pro¬ 
portions for side-hill work in rock. 

The size of cross-section should be large 
enough to give the required capacity when the 
canal is covered with ice to the maximum thick¬ 
ness. If the velocity is low, a considerable allow¬ 
ance should also be made for growth of weeds 
and grass. Fig. 151.—Canal Sec- 

618. Other Details. —The construction of im- 1ION 0N SlDE HlLU 
pervious banks follows the same general principles as laid down for 
reservoir construction. Side slopes in ordinary soils will vary from 
I to I for hard clay and gravel, to 3 to I or 4 to 1 for fine sana. 
The tops of the bank should be from I to 2 feet above the water-line. 
It is well to construct a berme just above the water-line, or at the 
original surface of the ground, above which the slopes of the bank 
may frequently be made steeper than below. If the soil is very porous, 
a lining of concrete or puddle may be necessary. Some canals have 
been lined with a layer of but 2 or 3 inches of concrete, placed on the 
earth and plastered with Portland-cement mortar. Fig. 152 illus- 



Fig. 152.— Santa Ana Lined Canal. 


trates a form of section used on the Santa Ana Canal, California. If 
a very heavy lining is required, it will usually be better to build a 
covered masonry aqueduct, as this avoids trouble from ice and protects 
the water from pollution. The presence of clay and silt in the water 
will tend gradually to reduce percolation. 















533 


CONDUITS AND PIPE-LINES. 


At sharp bends, and wherever the velocity exceeds the safe velocity 
for the material, some form of revetment is necessary. This may be 
merely a layer of gravel, or a paving laid dry or in cement, or a layer 
of concrete, according to the velocity of the water. If the general 
slope of the ground is too great for the canal, the fall may be con¬ 
centrated at a few points by dams, below which the channel must be 
protected against scour, as described in Chapter XVII. On side-hill 
work a ditch should be constructed on the upper side to carry off sur¬ 
face drainage. The lower side of the canal at such places will often 
consist of a masonry wall as shown in Fig. 15 I. 

Waste-weirs and sluice-gates should be provided at intervals along 
the canal to prevent flooding and to permit of rapid emptying. 
These wasteways should be located near some natural watercourse into 
which the waste-water can be conducted by suitable channels. The 
flow in the canal is regulated for the most part by sluice-gates at the 
head of the canal. These and other forms of canal gates are sup¬ 
ported either by masonry walls, or by timber framework. Stop-planks 
fitting into grooves in the masonry are suitable for weirs, and for gates 
which are but seldom operated. 

Canals are carried across valleys on trestles or bridges, or, in the 
case of short crossings, on embankments with a culvert or arched 
bridge beneath. Under-crossings are made by means of inverted 
siphons of pipe. 

A recently excavated canal for water-supply purposes is one 15,800 feet 
long, carrying the water from the new Wachuseti aqueduct of the Metropolitan 
Water-supply of Boston, down an old waterway to one of the old reservoirs. 
It is 20 feet wide on the bottom, with side slopes 3 to 1. To avoid too high 
a velocity two dams were built giving two moderate falls. Bermes at least 
10 feet wide were constructed on each side, and the slopes above were made 
not steeper than 2 to 1. Where dug through fine sand the canal was faced 
with gravel or riprap.* 

619. Flumes. —Where excavation for a canal is difficult, flumes of 
wood are often used for temporary works and for irrigation purposes 
on account of their low first cost. They are usually constructed with 
horizontal bottoms and vertical sides, but a more advantageous form, in 
which wooden staves are used for the lower portion, has recently been 
employed on the Santa Ana Canal in California. + A flume can be 
made much smaller than a canal on account of the high velocity of 6 


* Report Mass. Board of Health, 1895^ on the Metropolitan Water-supply. 
\ See Trans. Am. Soc. C. E., 1895, xxxm. p. 61. 






MA S ONR Y AQUEDUCTS . 539 

or 8 feet per second permissible. There is also much less resistance 
to flow, thus giving much less loss of head for like capacity. 

MASONRY AQUEDUCTS. 

620. Advantages of Masonry Acqueducts.— For conveying relatively 
large quantities of water over territory where the conduit can readily 
follow the hydraulic grade-line, the masonry conduit in cut and cover 
is a preferable form of construction. If properly constructed it is very 
durable, requires little attention, and if the topography is favorable it 
is much cheaper than large pipe conduits of iron or steel. Masonry 
is unsuited to withstand tensile stresses, hence it is not used to convey 
water under pressure. Combinations of steel and concrete may, 
however, be used for this purpose. Masonry conduits would not 
often be employed for cross-sections less than 10 or 15 square feet, for, 
unless the location be very favorable, their cost for such small sizes 
is likely to be greater than that of steel or iron pipes. 

621. Size of Cross-section, Velocity, and Slope. —The size of cross- 
section, the velocity, and the slope are interdependent, one of the last 
two elements being usually the determining factor. The velocity 
should preferably be such as to prevent deposit of sediment, which 
requires 2 \ to 3 feet per second average rate; and for brick or concrete 
masonry it should not exceed 6 or 7 feet per second. Higher veloc¬ 
ities may be allowed if stone masonry of hard material is employed, or 
if a lining of iron or steel is used. The question is usually determined 
by the available head between the terminal points of the conduit, or by 
the topography of the locality. If sufficient head is available, a smaller 
conduit will result if the velocity is made as large as the material will 
stand without danger of excessive wear. 

The circular form of cross-section gives the greatest hydraulic 
mean radius and therefore the minimum area of section, but this form 
is not the most economical in construction. For large aqueducts the 
form which experience has shown to be the best is that illustrated in 
Figs. 157 and 158. The hydraulic radius of this section is but little 
less than that of a circular section. 

Whatever the section adopted, the values of the hydraulic radius, 
velocity, and discharge for different depths of water should be tabu¬ 
lated for convenient use in computations. It will usually be the case 
that a conduit will flow only part full for the first few years, and the 
design should be made with reference to the fact that as the flow 
increases the velocity will increase. Kutter’s formula is usually em- 


540 


CONDUITS AND PIPE-LINES. 


ployed in calculations. The value of n to be used will vary with the 
character of the masonry about as given on page 246. The resistance 
to flow may be very greatly increased in a few years after the conduit 
has been put into use, by the formation of deposits or by organic 
growths. The capacity of the New Croton Aqueduct has diminished 
from such causes about 14 per cent in 9J years. 

622. Materials Employed. —Brick is the most suitable material for 
linings, and is commonly used also for the entire arch-crown. For the 
side walls and foundation, rubble masonry or concrete is employed. 
Concrete is eminently suited for this work, and in the Wachusett aque¬ 
duct of the Boston water-supply concrete with a brick lining is used for 
the entire structure, as shown in Fig. 158. Natural-cement concrete, 

1 : 2 : 5, is used for foundations and side walls, and Portland-cement 
concrete, 1 : 2 \ : 4J, for arches. Brick for linings should be hard- 
burned and dense, and should be laid in Portland-cement mortar. 
For places of great wear paving-brick in cement is a good substitute 
for granite. Concrete is better suited than either stone or brick for 
irregular forms and especially for light sections. It is not unlikely that 
a section will be developed consisting of a combination of steel and 
concrete that will be more economical than the forms now used. 
Such a combination has been suggested for a conduit for the Jersey 
City water-supply, and tests indicate that the section proposed has 
ample strength.* 

623. Form and Stability of Section. —The forces to be considered in 
designing a section are the pressure of the water, the earth-pressure, 



Fig. 153. 

Gallery, Vienna Water-works. 



Fig. 154. 

Small French Aqueduct. 


and the weight of the masonry. Besides being of sufficient strength 
the section must be of convenient form for construction and inspection, 
and it must be economical. For small aqueducts a rectangular form 


* Eng . News , 1900, XLIV. p, 142. 






















MASONRY AQUEDUCTS . 


541 


lias often been used, as in Figs. 153 and 154♦ the cover being of 
stone slabs or of arches. I he Manchester aqueduct is also of this 
general form (Fig. 155)- Sharp angles are, however, objectionable, 
and these can be avoided and an increased capacity obtained at little 
cost by building the bottom as an inverted arch. Such a form is also 
better suited to lesist any upward pressures. If there is lateral earth 
pressure, the sides will also be strengthened by curving them. These 



lr> RocK 


' In Compact Earth 



Fig. 155. 

Manchester Aqueduct. 


Fig. 156. 

Dhuis Aqueduct, Paris Water-works. 


modifications give rise to the horseshoe shape as commonly used for large 
conduits. To make the bottom of short radius, giving a circular or 
elliptical section, is not so convenient in practical construction, although 
to give head-room in small conduits the elliptical or oval section has 
been used (Fig. 156). 

In the case of small conduits built in compact earth, the water-pres¬ 
sure and the arch-thrust may be considered as largely resisted by the 
earth, Dut to insure this the back-filling up to the springing-line should 
be entirely of concrete (Figs. 155 and 158). In rock, a lining of one 
or two rings of brick, or of brick and concrete, is all that is necessary. 
In loose earth, and especially on embankments, the side walls should be 
heavy and have broad foundations. Little dependence can be placed 
upon the lateral thrust of the earth in an embankment, and experience 
indicates that in the settling of embankments there is a tendency for 
the walls to spread, and large longitudinal openings or cracks have been 
formed in aqueducts in this way. Iron rods imbedded in the founda¬ 
tion have been successfully used to prevent this. Several sections of 
the Croton and the Wachusett aqueducts are illustrated in Figs. 157 
and 158. 

The thickness of the arch is made about one-tenth to one-sixth the 
width of the opening, and of two, three, or four rings of brick or 
a corresponding thickness of concrete, depending on span and weight 

















542 


CONDUITS AND PIPE-LINES. 




In Compact Earth 


In Rock 


)n Loose Earth 



Timber Foundation and Drain. 

Fig. 158.—Sections of the Wachusett Aqueduct, Bost< 


































































MASONRY AQUEDUCTS. 543 

of covering. The arch may be designed as other arches. It is gen¬ 
erally segmental in form. 

The invert, in compact ground, is made only thick enough to. 
secure a firm and impervious bottom, two or three rings of brick or 
a thin layer of concrete with brick lining being usually employed. 
Even in an impervious rock an invert is desirable as giving a smoother- 
bottom for cleaning and inspection, and offering less resistance to flow. 
In soft foundations, or on embankments, the invert should be made 
thick, in order to be able to act as a beam and so aid in distributing the 
weight of the side walls, as in Fig. 159. A timber foundation and 



sometimes piling may be required on soft soils. Settlement must be 
reduced to very low limits, or cracks and leakage will result. 

624. Constructive Features. —It is unnecessary to state that in work 
of this kind the masonry must be constructed with the most careful 
supervision. In wet soils, drains should be built beneath the invert to 
enable the masonry to be laid without trouble from water. The drains, 
may be led into the conduit at a point lower down and the water per¬ 
mitted to flow through the completed portion. Concrete and stone 
masonry should be given one or two finishing coats of thin neat cement 
to secure imperviousness, the last coat to be finished as smooth as 
practicable. If carefully done, and no settlement occurs, the leakage 
will be slight. Cracks due to expansion and contraction are not likely 
to occur, as temperature changes are small. Gaugings of 7 miles of 
Croton aqueduct in tunnel showed a leakage of only 228,500 gallons 
per 24 hours. This portion was finished with a thin coat of Portland 
cement. 

Where built on embankment the greatest care must be used in 
constructing the earthwork in order to avoid settlement. The follow¬ 
ing is an extract from the specifications for the Wachusett aqueduct 
relating to embankment construction: 

“ The central portion of the bank, beneath the level of the highest part 
of the base of the aqueduct, to a width 8 feet greater than that of the base 











544 


CONDUITS AND PIPE-LINES . 


at such level, and to an added width of i foot for each foot below such level, 
is to be built with extreme care and with carefully selected earth; all stones 
larger than 2 inches in diameter are to be thrown out. The material is to be 
deposited and spread in horizontal layers not exceeding 3 inches in thickness, 
each layer to be sufficiently watered and very thoroughly rolled with a heavy 
grooved roller. From time to time during the construction of this portion of 
the embankment, and, if so required, three times after its completion, this 
portion shall be so thoroughly saturated with water that it will stand upon 
the surface. The building of the aqueduct upon such embankments shall 
not be begun until they have stood six weeks after completion, unless other¬ 
wise directed. ” 

The requirements for the remainder of the earthwork were some¬ 
what less severe. The embankments have in general a top width of 
14 feet, with side slopes of if to 1. They start from a base from which 
all soil and all other perishable matter are removed, and on sloping 
ground the base is stepped. If founded on soft material, such material 
must be removed or piles be used. Experience proves that with good 
material and careful work the settlement of embankments will be very 
slight. 

Trenches should not be back-filled until the cement has had time 
to harden considerably, and then it should be carefully done from 
both sides simultaneously. The evils of too hasty loading of the arch 
have been well shown by Mr. A. Fteley, by means of a device for meas¬ 
uring the deformations of the cross-section. The use of this during the 
progress of the construction of a large aqueduct showed a considerable 
settlement of the crown, due to too early loading. The diagrams also 
showed the insufficient strength of invert in yielding ground.* 

The aqueduct should be covered to a depth of 3 or 4 feet to prevent 
the formation of ice and to protect the masonry. Embankments 
should be given a slope of 1^ to 2 horizontal to 1 vertical, according 
to the nature of the material. They should be trimmed to a rounded 
outline and then sodded. 

625. Special Details. —Masonry aqueducts, like canals, should be 
provided with gates, wasteways, and overflow-weirs at intervals, to 
maintain the water-level, and to enable the aqueduct to be emptied in 
parts. Masonry aqueducts are not designed to flow under pressure, 
and to insure safety in this respect, long aqueducts will require the 
construction of waste-weirs. Gates should be constructed at the junc¬ 
tion of aqueduct with pipe-lines or siphons, and at terminal points. 
Intermediate wasteways or blow-offs are located near some natural 
watercourse, and should have a capacity, if possible, equal to that of 
the aqueduct. Fig. 160 shows one of the wasteways of the New Croton 


* Jour. Assn. Eng. Soc., 1883, it. p. 123. 






Fig. 161.—Undercrossing, Brooklyn Conduit. 

Culverts for crossing small streams, and bridges for larger ones, are 
a part of the design. Some of the most monumental works of history are 
the bridges which have been built for carrying aqueducts. Large aque¬ 
duct bridges are now seldom constructed, pipe-lines being substituted, 
but bridges of moderate size will still often be the more economical 
design. These are usually masonry structures, and, as in the case of 


MA SO NR Y AQUEDUCTS. 54 5 

Aqueduct and a stream-crossing at the same place, and Fig. 161 illus¬ 
trates an undercrossing of the Brooklyn conduit.* 


Section A B 

Fig. 160.—Blow-off and Culvert, New Croton Aqueduct. 


* Eng. News , 1891, XXV. p. 225. 

































































































































































































































546 


CONDUITS AND PIPE-LINES. 


embankments, special pracautions must be taken to prevent settlement. 
Experience with other structures of a similar character led the engineers 
of the Wachusett aqueduct to adopt certain special precautions in the 
construction of the Assabet bridge. This is a masonry structure 389 
feet long and of seven spans. The brick lining of the aqueduct was 
first covered with a coat of cement mortar, which was then painted. 
Sheets of lead weighing 5 pounds per square foot were then carefully 
cemented in place, coated with asphalt, and the interior lined with 
8 inches of brick. The roof is of brick arches on I beams, and is 
covered with cement and asphalt. 

Small streams are led under aqueducts through culverts, or through 
inverted siphon-pipes with gratings at entrance. 

626. Tunnels. —Tunnels frequently form a part of an aqueduct. 
The section adopted is usually the same as for the masonry portion, 
but the circular form may here be used. In unstable material a brick 
lining will be required. If a tunnel is unlined, the section should be 
increased by 1 5 to 20 per cent to allow for increased resistance due to 
the roughness of the surface. The unlined portion of the Wachusett 
tunnel is thus made about 21 per cent larger than the lined portion; 
likewise in the case of the Manchester aqueduct the increase in section 
is about 16 per cent. Mr. J. R. Freeman adopts for certain proposed 
aqueducts for New York City a value of n in Ivutter’s formula of .028 
for unlined tunnel and .014 for lined tunnel. He estimates that for 
large sizes the lined tunnel is actually cheaper for a given capacity 
than the unlined.* 

Tunnels are usually built to flow free, but sometimes are operated 
under pressure. Thus the Croton aqueduct tunnel is under about 125 
feet pressure for 7 miles, and under the Harlem River the head is 
about 425 feet, the hydraulic grade-line being there 120 feet above the 
river. The actual unbalanced water-pressure on the aqueduct lining 
would be the difference between the inside pressure and the pressure 
of the ground-water, which, at the river-crossing, would probably be 
measured by the level of the water in the river. If the ground-water 
pressure is in excess, there would be filtration into the tunnel. 

It appears to be difficult to secure good work in placing the back¬ 
ing of tunnels, and the defects in this respect are notorious in one or 
two large aqueducts. Recent experiments by Col. A. M. Miller, U. S. 
Engineer, have shown that cavities which are not easily filled with 
masonry in cement, can be filled dry and successfully cemented by 
forcing in grout under pressure.t 


* Report on New York’s Water-supply, 1900, p. 318. f Eng. News , 1899, xi.ll. p. 410. 





DESIGN OF PIPE-LINES. 


54 7 


627. Aqueducts of Vitrified Pipe. —As already described in the last 
chapter (page 521), vitrified pipe can well be used for small aqueducts 
nor under pressure. This pipe is considerably smoother than brick 
masonry, and for any given capacity will be more economical, at least 
for sizes up to 24 to 30 inches, and possibly for the 36-inch size. 

PIPE-LINES. 

The General Design. 

628. Material to be Employed.^ —The advantages of various materials 
have been considered in the last chapter. Summarizing briefly, it may 
be said that cast iron is especially suited for conduits of small or moder¬ 
ate size, and for places where frequent use of branches and specials is 
called for. Steel is especially suited for very large sizes, and for 
heavy pressures, and for lines in those situations where a light pipe is 
especially desirable. Wooden pipe is adapted for use in remote regions, 
for low pressures, and where the pipe is to be exposed. Vitrified pipe 
may be used for small sizes and very low pressures. 

629. The Profile. —The question of location has already been 
touched upon in a general way. in Art. 614. A pipe-line must follow 
in general the variations of the ground-surface, and such a location 
should be selected as will enable it to do so and at the same time 
give low pressures, that is, it should be kept as near the hydraulic 
grade-line as possible. If the pipe is made of uniform size, the hydrau¬ 
lic grade-line will be a straight line from one end to the other; but if 
it is not practicable to keep the pipe-line below a continuous grade¬ 
line at all points, an intermediate reservoir may be placed at the high 
point and the sections on either side designed independently. Several 
such breaks may evidently be advisable in some cases. If the inter¬ 
mediate points are too high for this arrangement, then a deep cut or 
a tunnel will probably be desirable. Small elevations above the hy¬ 
draulic gradient may be overcome by siphonage, but this will require 
special provision for the removal of air. In other cases pumping may 
be resorted to. 

If the pipe-line dips too far below a straight grade-line, it may save 
expense to break the grade in this case also, by means of an interme¬ 
diate reservoir so located as to give sufficient fall in the lower part of 
the conduit. Thus, in Fig. 162, AB is the grade-line with a pipe of 
uniform size, and ACB the gradient when a reservoir is inserted at C. 
The latter arrangement gives much the lower pressures. 


548 


CONDUITS AND PIPE-LINES. 


Overflows and equalizing reservoirs are advantageous for regulating 
the pressure in the pipe; and to permit of their economical construction 
it is desirable to have the pipe-line approach or cut the hydraulic grade¬ 
line occasionally. Plan and profile should be so laid out as to avoid 
sharp curves as much as possible, and the curves used should conform 
to certain adopted standards. In deep valleys and gorges it will often 



be best to carry the pipe for a short distance on a trestle or bridge, 
thus avoiding sharp curves and at the same time shortening the line. 

630. Pressures to be Assumed —The water-pressures in a pipe-line 
are measured by the ordinates to the hydraulic grade-line, which has 
a slope depending upon the frictional loss. When the water is station¬ 
ary the hydraulic grade-line is horizontal and the pressures will be the 
same at all points at the same level. When flowing, the pressures will 
be much reduced at certain points. If a pipe-line is so designed that 
the lower end is closed at times, the pressures must be assumed to be 
static, i.e., measured from a horizontal hydraulic grade-line; but if it 
is so arranged that the water will always have free egress, then the 
pressures will be measured from the sloping hydraulic grade-line, and 
much will be saved in cost of pipe. In practice, the second condition 
is often practically obtained by placing small reservoirs and overflows 
on the hydraulic grade-line at intervals where the pipe-line rises close 
to this elevation. Each section of pipe between consecutive reservoirs 
may then be operated in the ordinary way and designed for the static 
pressure. This gives a pressure-line consisting of a series of horizontal 
lines. The method of designing for a sloping hydraulic grade-line 
requires that no part of the line can possibly be closed except at the 
extreme upper end. In this case also it is well to have overflows at 
various points along the pipe-line. Obviously both methods of design¬ 
ing may be employed for different sections of a conduit. 

An example of a combination of both methods is the Rochester 
conduit, the profile of which is shown in Fig. 163. The pipe is a 
38-inch steel pipe 26i miles long. In the middle of a 171-mile sec¬ 
tion an overflow-tower is connected to the pipe, and is always kept 


DESIGN OF PIPE-LINES . 


549 


open, thus limiting the pressures on the upper half to those due to 
the hydraulic grade-line. A waste-pipe leads to a near-by creek. 
The lower half is designed for static pressure and is provided with 
gates in the usual manner. 

In the case of large pipe-lines not connected with distributing 
systems the pressure to be considered in the design need not be much 



increased for the item of water-hammer. This is especially true of 
pipes ending in reservoirs and operated with open ends. 

631. Calculation of Size of Pipe. —Where the total available head is 
fixed, the size required for any given capacity is readily determined. 
If the head is very small, the size required will be relatively large, and 
it may be more economical to use pumps, with a smaller pipe-line, de¬ 
signed as explained below. In case the water contains suspended 
matter, it is desirable to maintain a self-cleansing velocity of 2 to 2^ feet 
per second, otherwise the sediment must be blown out at frequent inter¬ 
vals. If the line is divided into sections by reservoirs or overflows, the 
size of each section is determined independently of the others. 

632. Economical Size of Pipes where Pumping is Required .—If the 
loss of head is not fixed, as is the case where the pressure is supplied 
by pumps, the size of pipe should be such as to make the total yearly 
expense a minimum. If the cost of various sizes of pipe is known, and 
the cost of pumping per unit of work done, the problem can readily be 
solved by a few trials. 

In most cases the possible variation in pipe would not seriously 
affect the design of the pumps, and the cost of fuel would be about the 
only item affected by a small change in head. The additional cost 
would then be small. In the case of very long force-mains, however, 
or pipe-lines with several pumping-stations, nearly all items of expense 
would be affected by a change in size of pipe. 









550 


CONDUITS AND PIPE-LINES. 


As this problem is of common occurrence in connection with dis¬ 
tributing systems as well as pipe-lines, an approximate general solution 
for cast-iron pipe will be given, from which a good notion of the 
economical velocities for various sizes of pipes can be had. 

From an analysis of Weston’s tables and other data relating to the 
cost of cast-iron pipe, it is found that the cost of pipe, laid, is approxi¬ 
mately given by the formula 

c — 20 + 2 ad uss , .(i) 

in which c — cost per foot in cents, 

a — cost of iron in cents per pound, 
and d — diameter of pipe in inches. 

If in eq. (31), page 230, we express d in inches instead of feet, we 
have, for the velocity of flow in pipes, 

^ / d\% ± ,54 

v = 76.28^—j s\ = 13 d 7 s Y , .(2) 

in which v — velocity in feet per second, and 
s — slope of hydraulic grade line, 

= loss of head in feet per foot. 

From eq. (2) we get 

7 

v* 

s = o.oii -|.( 3 ) 


We also have the general relation 


/ d \ 2 

Q = v - i *\~) .(4) 

Then from eqs. (3) and (4) we have 

Qa 

s — 100 . (5) 


Let b = yearly cost of pumping 1 cubic foot per second 1 foot high, 
and Q — volume pumped per second. Furthermore, let r — rate of 
interest plus rate of depreciation of pipe-line. The total yearly cost 
of pipe and pumping, per foot of pipe, will then be 


A — bsQ + cr — bsQ + 20 r -f 2 ard , 5S . 





DESIGN OF PIPE-LINES. 


551 


Substituting the value of ^ from eq. (5), we have 

Q 2 75 

A = 100^-^- 5 -f- 20 r + 2 ard U5S .(7) 


Differentiating with respect to d, etc., we find that for a minimum 
value of A 


d = 



• • • 



that is, for any given values of b and a the diameter should vary 
with Q- 44 . 

To express this relation in terms of velocity, which is a more con¬ 
venient form, we may substitute from (4); whence we have, for the 
economical velocity, 


v = 


30 




The cost of pumping is ordinarily expressed in terms of cost per 
1,000,000 gallons lifted 1 foot high. This will vary largely in different 
plants, but the cost of additional lift will seldom exceed 3 to 4 cents 
per million-gallon foot, and in large plants will not exceed 2 cents. 
The total cost of pumping in large plants is usually from 3 to 5 cents. 

Table No. 77 gives various values of v as computed from eq. (9) 
for various costs of pumping. The cost of pipe is taken at 1 cent per 
pound, interest-rate 4 per cent, and a depreciation of pipe-line of 1 per 
cent per year. For other values of the cost of pipe, (a), or of interest 
plus depreciation, (r), multiply the value of v given in the table by a 136 



If the pumping is done at a variable rate, then the maximum 
velocity should be made somewhat greater than the value given in the 
table. If, for example, the pumps are operated for half the time at a 
rate Q , then the value, of b will be equal to the total yearly cost divided 

by the rate Q and by the head, and will hence be less than if a rate — 


were maintained for the entire year at nearly the same total cost. 
The resulting value of v will therefore be greater; in the assumed case 
it will be equal to the value given by the table multiplied by 2 36 or by 


i-3- 

For other than cast-iron pipe the actual cost will be different from 
the cost here assumed, but the variation in cost of pipe with size will 




552 


CONDUITS AND PIPE-LINES. 


be proportionately about the same, so that an approximate value for 
velocity can be found by using the table with such a cost of cast iron 
as will give the correct cost of some one size of conduit. As in all 
cases of maximum and minimum, a considerable change in the value 
of the variable when near to the correct value will affect the result but 
slightly. Another factor which usually enters is the gradual increase in 
the quantity of water which is to be pumped, so that the pipe must at 
first be made too large for economy. 

TABLE NO. 77 . 

ECONOMIC VELOCITIES IN CAST-IRON MAINS WHEN THE COST OF PIPE IS I CENT PER 
POUND, AND THE COST OF ADDITIONAL LIFT IS 2, 4 , AND 6 CENTS PER MILLION- 
GALLON-FOOT. INTEREST RATE PLUS DEPRECIATION — 5 PER CENT. 


Size of Pipe. 


Cost of Pumping 
1,000,000 gal. 

1 foot high. 

4-in. 

6-in. 

8-in. 

12-in. 

16-in. 

24-in. 

30-in. 

36-in. 

48-in. 

60-in. 

Velocity in Feet per Second. 

2 cents. 

I . 6l 

1.82 

i -95 

2.19 

2-37 

2.65 

2.82 

2.98 

3-23 

3-43 

4 cents. 

1-25 

1.41 

1.52 

1.70 

I.85 

2.07 

2.20 

2.32 

2.51 

2.67 

6 cents. 

i .oS 

1.22 

1 • 3 1 

I.47 

I .60 

1.78 

I . 90 

2.00 

2.17 

2.31 


If pipe costs if cents, multiply above values by 1.08. 


if I-I5. 

If the pressures in a pipe-line vary greatly, the most economical 
size will not be the same for all sections, but will vary a little, being 
the smallest under the heaviest pressures. 

Construction. 

633- Plan and Profile. —In preparing a design, an accurate map and 
profile should be made to a large scale, on which should be shown the 
exact location of the pipe, the radius and length of each curve, location 
and amount of angles or bevels, and the position and size of valves and 
other appurtenances. The various sections of pipe and the special 
forms can then be numbered to correspond with the location on the 
map so that they can be readily sent to their proper places. 

634. Trenching —Trenches for water-pipe are not usually deep 
enough to require much bracing or sheeting, the depth being ordinarily 
only sufficient to give the necessary covering. Deep trenches will, 
however, be required occasionally, as where the pipe-line crosses a high 
ridge extending above the hydraulic gradient. The methods of 
































CONSTRUCTION OF PIPE-LINES. 


553 


sheeting and bracing, and of trenching, are the same as used for sewer 
work, and will be found fully described in works on sewerage. In wet 
ground, only a short section of trench should be opened at once, in order 
to keep the inflow of water as low as may be. In rock, the trench must 
be carried 3 to 6 inches below the proper grade and the space refilled 
with sand or fine material to give a proper bedding for the pipe. Bell- 
holes for cast-iron pipe must be excavated wide enough to give plenty 
of room for making a good joint. All existing pipe-lines and other 
structures must be carefully supported or removed. 

635. Foundations. —Where the material is too soft to give a good 
bearing, it may be necessary to use artificial foundations. These may 
consist of blocks placed on stringers, or of piling, with caps on which 
the pipe may rest. When full of water the pipe will weigh but little, 
if any, more than the soil displaced, so that there is little tendency 
for it to settle after the back-filling has become compact. A foundation 
is necessary, however, to keep the pipe in place during construction 
and to hold it rigid against unequal pressures. For large valves and 
other heavy parts, special foundations of concrete are likely to be 
needed. To assist in getting large pipe to grade, it is convenient to 
support it on wooden blocking and wedges, two blocks being used 
under each section. After laying, the trench should be well filled 
underneath the pipe by suitable material. At sharp curves and angles, 
buttresses of concrete or stone masonry should be built to prevent dis¬ 
tortion of the line by the water-pressure. Anchorage masonry is also 
desirable at intervals in case the grade is very steep. 

636. Laying of Pipe. — Cast-iron Pipe .—The laying of cast-iron 
pipe is usually begun at a valve or special. Small pipe up to 6 or 8 
inches in diameter is easily handled without a derrick, the sections being 
lowered into the trench by two or three men. In laying, care should 
be taken to enter the pipe to its full depth and to see that there is, 
sufficient joint-space all around. The pipe should have been inspected 
for eccentricity, and the joint-room should not vary more than T V inch 
from the required dimensions. The spigots should be adjusted by 
wedges to give a uniform joint-space. The packing of jute or other 
material is inserted and thoroughly packed with a thin yarning-iron. 
If special strength is not required, this packing may nearly fill the space 
back of the enlargement or V-shaped space in the bell. The remain¬ 
ing space is filled with molten lead. In pouring the joint the lead is 
guided into the space by a jointer, commonly made of clay formed 
around a length of rope. This is placed about the pipe so as to press 
against the hub, except at the top, where an opening is made for pour- 


554 


CONDUITS AND PIPE-LINES . 


ing. Patent jointers are better for large pipe and difficult work. After 
pouring, the lead is loosened somewhat from the pipe by means of a 
chisel and set up by calking-iron and hammer. To do good work 
there should be plenty of room around and under the pipe. In wet 
trenches and with small pipe, two or three sections may be joined 
before lowering. To handle large pipe, various forms of derricks are 
employed, the three-legged form being commonly used. Fig. 164 



Fig. 164.—Pipe-derrick, Baltimore, Md. 

(From Engineering Record , vol. xxxvii.) 

illustrates a specially designed derrick of the Baltimore Water-works, 
made for handling pipe up to 16 inches in diameter.* 


* See also Eng. News, i 8 q 6 , XXXV. p. 339 , for illustration of another form. 




















































































































CONSTRUCTION OF PIPE-LINES. 


555 


637. Steel Pipe .—Riveted pipe should be connected up in as long 
sections as practicable before being transported to the trench, so that 
as much of the riveting may be done by power-riveters as possible, 
bor this reason it will be desirable on large works to establish a rivet¬ 
ing and dipping shop not far from the pipe-line. In transportation and 
construction the greatest care should be taken to avoid injuring the 
coating. When placed in the trench the pipe should have an even 
bearing on firm soil or on blocking, and should be well supported while 
the joints are being riveted. The riveting is usually done by hand, but 
power-riveters have been used in a few cases. These are made in two 
parts: (1) a ring which fits around the pipe and forms the support; and 
(2) the power appliances, which are placed on the inside. Two rivets 
on opposite sides may be driven at the same time. Power-riveters 
require a much larger excavation to enable them to operate, but they 
are desirable where the rivets are large.* The percussion pneumatic 
riveter, which is largely used in ship-building and similar work, would 
seem to be well adapted for this work. 

After riveting, all field-joints should be calked, and these and all 
other abraded places painted. Some recalking may be needed after 
the pipe is tested. 

638. Wooden Pipe .—Points to be specially observed in the con¬ 
struction of wooden-pipe lines are care in the selection of the timber, 
proper coating of the bands and spacing of same, and proper cinching. 
Spacing of bands should be fully indicated on the profile. In making 
the pipe, the staves for the lower half are laid in a cradle of circular 
form, and those for the upper portion are supported on rings. The 
pipe can be built in sections, which may readily be connected by cutting 
the closing staves slightly too long and springing them into place. 
Sharp angles cannot be followed, and even to make easy curves the 
pipe has to be forced out of line by means of jacks and braced in place 
until the construction has progressed considerably. 

639. Testing and Inspection.—The pipe as completed should be 
tested in sections of 1000 feet, or thereabouts, by hydraulic pressure. 
For this purpose the ends are closed with specially-made blanks, 
which are provided with pipe-fittings, valves, and gauge attachments. 
The pressure used should be somewhat higher than that which will 
obtain in regular service. It may be inconvenient to leave a steel pipe 
entirely uncovered until the test is made, on account of trouble due to 


* See Eng. News, 1898, xxxix. p. 170, and Trans. Am. Soc. C. E., 1897, xxxvm. 
P« 264. • 





55 ° 


CONDUITS AND PIPE-LINES. 


tempeiature changes, but the field-joints at least should be left open to 
inspection. Wherever leaks are found the pipe should be recalked. 

After the construction is completed a pipe-line should, if possible, 
be inspected in the interior throughout its entire length. By suitable 
means comparatively small pipes can be thus inspected. A 30-inch 
pipe-line at Syracuse was inspected by a man passing through the pipe 
by the aid of a special car. 

640. Covering of Pipes. —Except in mild climates a conduit will 
need to be covered to prevent the water from freezing; and even in 
warm climates it will usually be desirable to cover conduits of iron or 
steel to protect them from extreme variations of temperature. The 
recently constructed Coolgardie pipe-line, as first proposed, was to be 
left exposed, on account of the objectionable character of the soil, but 
later it was decided to cover it. Iron and steel would be more durable 
if exposed, as they could then be kept painted, but much expense 
would be involved in the construction of expansion-joints, and there 
would also be more danger of interruption of the supply. Not so much 
objection is to be made against exposed wooden conduits, and some 
have been so constructed. In a wooden pipe there is no trouble from 
expansion, and the water is not so greatly affected by temperature 
changes. 

The depth of covering to protect pipes against freezing, in the case 
of the large conduits under discussion, need not be more than 3 or 4 
feet in the northern part of the United States. (See also Art. 754.) 
A covering of 2 or 3 feet is sufficient to protect them from injury by 
ordinary traffic. The maximum allowable depth of covering will 
seldom be reached, but for very large pipes additional strength should 
be given when the lightest pipe would otherwise be used, if the depth 
of filling exceeds 15 or 20 feet. For the reasons pointed out in Art. 
576 the back-filling should be done with great care up to the top of 
the pipe, the material being placed and tamped in 4- to 6-inch layers. 
This is especially important for light steel pipe. If the pipe is located 
in paved streets, the back-filling must be thoroughly tamped through¬ 
out (Art. 756). 


Appurtenances and Special Details . 

641. Provision for Expansion and Contraction. —In the case of cast- 
iron pipes, expansion and contraction are sufficiently provided for by 
the flexibility of the lead joints, unless the pipe be exposed for long 
distances. In riveted steel pipe, ordinarily no provision for expansion 
is made, the pipe being therefore stressed accordingly. To resist the 


APPURTENANCES OF PIPE-LINES. 557 

forces developed will require heavy anchorages at the ends of pipes 
and at junctions with masonry portions, or else expansion-joints must 
be used at those places, as has been done in some instances. Valves 
and special castings must also be made strong enough to resist this 
force of expansion. (See page 501.) Exposed sections of pipe, if of 
any considerable length, should be provided with expansion-joints, but 
as these are, for large pipe, somewhat expensive and difficult to make 
operate satisfactorily, they should be avoided if possible. For small 
pipe, and at points readily inspected, the ordinary stuffing-box with 
gland, etc., answers the purpose. For larger pipes various other forms 
have been devised, some of which are illustrated in Fig. 165. Fig. 
165^ illustrates a joint which has been used to a considerable extent in 





Fig. 165.— Forms of Expansion-joints. 

Paris with good satisfaction. Figs, b and c illustrate joints wholly of 
metal which have been employed to some extent.* All these are 
designed for large pipes. 

642. Manholes.— Manholes should be provided in large pipe-lines 
at intervals of 500 to 2000 feet, and particularly at depressions and 
near valves. They are usually of cast iron of oval form, about 18 or 
20 inches long by 12 or 14 inches wide. They are bolted to cast-iron 
flanges, which are cast with or bolted to the pipe. Where it is likely 
that mechanical scrapers may be used to clean a pipe, long removable 
covers or hatch-boxes should be built at intervals to admit the scraping- 
machine. (See Chapter XXIX for description of such machines.) 

* Eng. News , 1899, XLI. p. 406. See also large expansion-joint in Eng. Record , 
1899, xl. p. 156. 





















































558 


CONDUITS AND PIPE-LINES. 


643. Stop-valves. —To enable a pipe-line to be readily inspected 
and repaired, stop-valves should be inserted at intervals of 1 or 2 miles, 
and especially at important depressions and summits. Otherwise to 
empty and refill a long conduit would require several days. In the 
case of breakage, the water can be shut off at the nearest valve, and 
any considerable waste or serious damage be prevented. Large valves 
are expensive, and just as an increase in the cost of pipe will decrease 
the economical size of pipe, so in the case of valves, a size considerably 
smaller than the pipe can often be used with good economy. The 
cost decreases rapidly as the size decreases, while the loss of head due 
to the contraction, if made with suitable reducers, is not large. The 
best size can readily be calculated from cost of valves, cost of reducers, 
increased friction in smaller pipe, and cost of pumping or value of 

9 

head. An advantage of the small valve is that it is much more easily 
manipulated, and in some cases it may be desirable to hold to sucli 
sizes as can be operated by one man without the use of special gearing. 
An example of such an arrangement is in the connections of the large 
pipes of the East Jersey conduit, where a number of 16-inch pipes with 
16-inch valves were used. 

Valves up to about 16 inches in size are usually operated direct. 
Larger valves are operated by gearing, or by hydraulic power, the 
cylinder for the latter being constructed as a part of the valve. Large 
valves are usually provided with by-passes which are opened first, 
so that the pressures on the main valves are more nearly balanced. 
The force required to move a valve can be roughly calculated if we 
know the pressure and weight of valve-disks. The necessary gearing 
for manual operation can then be calculated. Very large valves are 
sometimes divided into two or more parts to give easier handling, and 
some are so arranged that when operated a small secondary valve is first 
opened which acts like the by-pass to reduce the amount of unbalanced 
pressure. 

Valves of all kinds and designs are furnished by various special 
manufacturing concerns. Fig. 166 shows an ordinary single-disk 
valve. Fig. 167 shows a large valve with gearing and by-pass such 
as is used on the Boston water-works. Valves for water-works should 
have double-faced disks, which should seat readily and accurately. 
Many forms are made with two disks which adjust themselves to the 
seats. All sliding surfaces should be faced with bronze, and the stems 
should also be of this material, and carefully proportioned as to 
strength. The waterway should not be obstructed when the valve is 
opened. All parts should be readily removable. Valves should be 


APPURTENANCES OF PIPE-LINES. 


559 



Fig. 166.—Gate-valve 
with Single Disk. 





Fig. 168.— Valve-box, Syracuse Water-works. 

(From Trans. Am. Soc. C. E., vol. xxxiv.) 








































































































































































CONDUITS AND PIPE-LINES. 


'560 

thoroughly tested for leakage from each side with valve closed, and 
again tested with the valve open. 

Small valves (up to 16 or 20 inches) are placed vertical, with stems 
protected by cast-iron valve-boxes or by masonry vaults. Large 
ones are placed horizontal, with the operating mechanism surrounded 




Vault for 30- to 40-inch Valves. 

Fig. 169.— Valve-vaults, Baltimore Water-works. 

(From Engineering Record , vol. xxxvii.) 


by a masonry vault or manhole. The standard valve-box used at 
Syracuse is illustrated in Fig. 168, and in Fig. 169 the valve-vaults 
used at Baltimore.* 

644. Air-valves. —At every summit of a pipe-line and at shut-off 
valves there should be placed an air-valve to permit the escape of air 
on filling, the entrance of air on emptying, and frequently the escape 
of air which may gradually accumulate at summits. The first and 
second objects are readily obtained automatically, and the third often 
is. Air-valves are of various design, a form known as the Brooks 
Automatic Valve being illustrated in Fig. 170. This form consists of 
a brass disk-valve supported on a spindle and opening inwards. When 
there is no water in the pipe the valve remains open, but when the 
water reaches the valve as the pipe is filled, it closes quickly by reason 


* Eng. Record, 1898, XXXVII. p. 143. 


















































































































































































































































appurtenances op pipe-lines . 


561 


of the buoyant effect and the velocity of the escaping water. A form 
is often used in which a brass ball constitutes the valve.* For large 
pipes a cluster of small valves is employed, and it is well to have them 

so arranged that they will not close simul¬ 
taneously. The area of air-valves is deter¬ 
mined from considerations of quick filling, and 
sometimes also is calculated to be sufficiently 
large to admit air fast enough to prevent ex¬ 
cessive vacuum in case the pipe should be 
broken. In distributing systems, hydrants at 
summits can usually be used as air-valves. 

At sharp summits, and with low velocities 
and pressures, air will be apt to accumu¬ 
late and give trouble unless removed, especi¬ 
ally in the case of force-mains. Air can 
be removed by hand-operation of valves of 

the form already des¬ 
cribed, or by automa¬ 
tic valves. A com¬ 
mon form of this type 
of valve is illustrated 
in Fig. 171. It is so 
proportioned that 
when air collects in 
the chamber and the float is no longer supported by water, the valve 
opens and permits air to escape till the water again rises to the float. 
It is necessarily a very small valve, and not well suited for the other 
purposes already mentioned. + The Engineering Commission of the 
Coolgardie pipe-line recommended that at important summits the pipe 
should be made of twice the ordinary size, so as to facilitate the collec¬ 
tion of air. 

An air-valve is usually connected to the main pipe by means of a 
short branch, which is provided with an ordinary gate-valve so as to 
permit the removal of the air-valve for repairs. Air-valves must be 
well encased and protected from frost. 

645. Blow-off Valves. —At all depressions, blow-off valves should 
be provided, the waste-pipes from which should be led to a sewer, 
stream, or drainage-channel. These valves need be only about one- 
third the size of the main pipe. 




Fig. 171. 

Automatic Air-escape 
Valve. 


* For other designs see references 3, 6, and 7, p. 574. 

f See Eng. Record , 1899, XXXIX. p. 493, for description of large automatic air-valve. 














































562 


CONDUITS AND PIPE-LINES . 


646. Self-acting Shut-off Valves.— Several English pipe-lines have 

been provided with valves so arranged that in case of accident to the 
pipe they will gradually close and so prevent loss 01 water and the 
destruction of property by flooding. In the device used, a lever carries 
at one end a small disk placed in the centre of the pipe. If the velocity 
of the water exceeds a certain amount, the pressure on this disk moves 
the lever, thus releasing a weight which in turn operates a butterfly 
valve in the main pipe.* 

647. Check-valves.—These are introduced at points where a break¬ 
age would permit a large loss of water by backward flow, such as at 
the entrance to reservoirs, at the foot of long upward inclines, and in 
force-mains just beyond the pumps. Their use in connection with the 


circulation in reservoirs is mentioned in Art. 
707. Fig. 172 illustrates an ordinary check- 



M valve for small pipes. For pipes larger than 


24 to 30 inches a diaphragm or valve-plate is 
cast in an enlarged section of the pipe, and a 


number ol small valves attached to this plate, 

valves usually exceeding 



that of the pipe. A small by-pass is also 
provided to avoid heavy water-hammer. 


Fig. 172.—Check-valv . 


648. Pressure-regulating Devices.—Various methods of automatically 
regulating the pressure are employed in different places. One very 
desirable method of regulating the pressure in a long conduit is by 
means of reservoirs and open stand-pipes, as already noted (Art. 629). 
These structures must be provided with overflows, and if the demand 
is quite irregular and the stand-pipe small, much water is likely to be 
wasted. This waste can be avoided and the flow adjusted to the 
demand by the use of the balanced float-valve, described on page 
452.t By this means the level in the reservoir may be kept constant 
by varying the opening in the preceding section of pipe. This method 
is applicable where a pipe-line is divided into several levels, or where 
a low-level district is served from a high-level source, but the section 
of pipe-line leading to such valve must be designed for static pressure. 

By suitable arrangements the balanced valve may be used also as a 
pressure-regulator, or pressure-reducer, without the interposition of a 
reservoir. To accomplish this the valve (see Fig. 135, page 455) may 


* Proc. Inst. C. E., vol. cxxvi. p. 2. 

f See description of special arrangement of such a valve, in Eng. News , 1898, 


XL. p. 158. 




















APPURTENANCES OF PIPE-LINES. 563* 

be operated by a small piston, d, acting in a closed cylinder. On one 
side of the piston this cylinder is arranged to communicate with the 
main pipe at whatever point the pressure is to be regulated. Upon the 
other side of the piston a spring acts in opposition to the water- 
pressure, which spring may be adjusted to any given tension. So long, 
then, as the pressures of the water and spring are equal no movement 
takes place, but as soon as the water-pressure exceeds that of the 
spring the valve is moved, which either increases or decreases the 
discharge as the case may be, and again brings the pressure down to 
the normal amount. A flexible diaphragm of thin metal may be used 
in place of the piston. 

Safety-valves, or pressure-relief valves, are occasionally used at the 
ends of long pipe-lines or wherever water-hammer is especially to be 
feared. They are simple disk valves opening outwards and held in 
place by springs which are adjusted to the water-pressure. They 
should be of large section and designed with reference to the principles', 
discussed in Art. 279, page 242. They take the place of air-chambers, 
and are more convenient at points where air-chambers could not readily 
be kept full of air. The water which passes through them at times of 
excessive pressure is of course wasted. The balanced valve can also- 
be readily used as a safety-valve by the method described in the pre¬ 
ceding paragraph.* 

649. Terminal Arrangements.—The upper end of a gravity pipe-line- 
is usually enclosed in masonry and provided with a sluice-gate or 
valve. At this point it is also desirable to have a weir or measuring- 
sluice. If pumps are employed, then a Venturi meter is a valuable 
device for measuring the flow. The lower end of a pipe-line usually 
terminates in a reservoir, where again valves are provided and where- 
connections may also be made directly with the pipe system. In case: 
the pipe-line is designed according to the hydraulic grade-line, no 
valves should be placed here, or if so placed, should be interlocked with 
waste-valves, so that the latter must be open before the former are 
closed. Such interlocked valves were used on the East Jersey pipe¬ 
line. 

Intermediate stand-pipes and reservoirs at the hydraulic grade-line 
may be merely short open pipes placed vertically, or laid up an 
adjacent hillside till they reach the proper elevation and where provision 
is made for overflow; or they may be larger or smaller reservoirs, 
according to the necessity for storage. It may be better and more 

* See details of such a valve used on the East Jersey pipe-line. Eng. News y 
1893, xxx. p. 24. 





5 6 4 


CONDUITS AND PIPE-LINES. 


convenient to store water in three or four reservoirs than in a single 
one. Rochester has two such reservoirs. Liverpool has six reservoirs on 
a 67-mile pipe-line, of capacities ranging from million to 650 million 
gallons. One advantage of large reservoirs is that the pressures are 
kept more constant without overflow, or with a less frequent adjustment 
of valves. Automatic valves may be used as described in Art. 648. 

650. Crossings.—In crossing under other structures, such as rail¬ 
ways, buildings, sewers, etc., special precautions should be taken to 
avoid all danger of future breakage. Pipe of extra strength may be 
used, or added strength given by a bed and covering of concrete. 
Large pipe-lines should be divided into two smaller ones for safety, 
with valve-connections at the ends. In very important cases the pipe 
may be laid in a subway so as to permit of repairs as readily as else¬ 
where. Streams are crossed either on bridges, or by laying the pipe 
beneath the stream-bed, or by the use of a subway as above mentioned. 
At Cleveland, Ohio, several crossings of narrow navigable streams have 
been changed to tunnel-crossings so as to permit of repairs. These 
tunnels are about 600 feet long and 9J feet in diameter, and are located 
78 feet below the street-surface. They end in vertical shafts provided 
with manholes. The pipes are of steel, 48 inches in diameter, the 
vertical sections of which are supported upon I beams built in the shaft. 
Expansion-bearings are provided at the bottom, and the horizontal 
portions are supported on saddles 6 feet apart.* Many examples of this 
form of crossing exist in European works, such as the Mersey crossing 
of the Liverpool aqueduct, and the crossing of the Seine at Paris. 

In this country the common practice in crossing a stream is to lay 
a cast-iron or steel pipe below the stream-bed, or else to employ a 
bridge-crossing. Where no bridge already exists the former will 
ordinarily be the cheaper, and in many cases, as in navigable channels, 
a bridge could not be permitted. In other cases it may be cheaper to 
build a bridge especially for this purpose, as in rocky canyons and 
narrow gorges. At the angles at ends of bridge- and submerged 
crossings special care is necessary to keep the pipe from separating at 
the joints. 

651. Bridges.—If the pipe-line crosses an existing bridge, it will 
usually be convenient to support it beneath the flooring. Where a 
bridge is built for the purpose, no floor-system is put in, but merely 
suitable straps or stirrups to support the pipe. Steel or wood-stave 
pipe may be used for short spans without other support than that fur- 


* Eng. Record , 1898, xxxviu. p. 449. 




EXPOSED PIPES. 


565 ; 


nished by the pipe itself. A steel pipe £ inch thick, full of water, will,, 
at a fibre-stress on gross section of 10,000 pounds per square inch, 
span a length of about 65 feet, if the tendency to buckle is not taken 
into account. This span-length is nearly independent of the diameter 
of the pipe, varying directly with the thickness of the material; but 
with large diameters the allowable stress would have to be much 
reduced, or else provision made to stiffen the upper plates of the pipe.. 
The pipe can readily be stiffened by the use of angles riveted along 
the upper surface, and also by placing the longitudinal seams near the 
top. If a pipe is used as a bridge, the circular seams must be designed 
for the extra stress involved. Expansion can be provided for in such 
a bridge by resting the pipe at one end in a saddle which is sup¬ 
ported on rollers. An expansion-joint is then placed just back of this; 
saddle. A pipe bridge would be cheaper than a separate structure 
even if the metal had to be much thickened to give the necessary 
strength. Trussing can also be applied so that the pipe will act 
only as a compression member.* Wooden-stave pipe has been used 
to span distances of over 100 feet by bracing two lines of pipe together 
and curving them in the form of an arch.f The strength of wooden 
pipe would depend upon the frictional resistance of one stave sliding 
on another. It is found in practice that a stave-pipe is very strong and 
rigid. 

652. Protection of Exposed Pipes. — The amount of protection 

« 

required to prevent freezing on bridges, or at other exposed places, 
depends upon the size of pipe, the amount of circulation during periods 
of minimum flow, the temperature of the air and the water, and upon 
the length of the exposed portion. No general rule can be given. 
Usually the water is from surface sources, and its temperature in winter 
will be but little above the freezing-point, unless it should pass for long 
distances in deep trenches. The temperature of the water will change 
very slowly in large pipe-lines, and in the case of pipes 2 feet or more 
in diameter special protection would seldom be needed at crossings of 
ordinary length, if the water has at all times some movement. A 
wooden pipe possesses much advantage in this respect over pipes of 
iron. 

Small lines, especially distributing-mains, require protection. This 
is usually furnished by placing the pipe in a wooden box and filling 
around it with some non-conducting substance, such as sawdust, 


* See example in Eng. Record, 1892, XXV. p. III. 
f Trans. Am. Soc. C. E., 1894, xxxi. p. 135* 




566 


CONDUITS AND PIPE-LINES. 


mineral wool, asbestos, hair-felt, and the like. A mixture of plaster 
of Paris and sawdust has been used with good results. Any packing 
to be effective should be kept dry. The packing is often arranged to 
give one or more dead-air spaces around the pipe to aid in preventing 
radiation. 

Materials such as above mentioned act to retain the heat of the 
water; but if the water is already near the freezing-point, they are not 
very efficient. Some method of applying heat may be desirable. 
Mr. S. E. Babcock has successfully solved this problem in the case of 
an exposed pipe at Little Falls, N. Y., by the use of wool waste as 
packing. This material contains a small amount of oil and gradually 
decomposes, thus giving off a small amount of heat. It was found 
necessary to renew this packing in five years, but the expense was 
small.* 

C53. Submerged Pipes.— Tarious methods are employed in laying 
pipes beneath watercourses. In the case of small streams the usual 
method is to employ a coffer-dam and lay the pipe as on dry land. 
Where the water cannot readily be excluded in this way the pipe must 
either be put together before lowering in place or must be laid by 
divers. Submerged pipe should, as a rule, be laid in a trench and 
carefully covered to prevent injury by waves, drift, ice, boats, etc. 
The trenching is done by dredging, and any drilling and blasting which 
may be necessary can be done from platforms or from anchored barges. 
In the case of at least one pipe-line the trench was made by the 
scouring action of the water, which was forced to flow beneath the pipe 
as it was gradually lowered into place. + The trench should be formed 
to line and grade, or at least an accurate profile of the same should be 
taken. 

Various special details are used in submerged-pipe laying, such as 
the various forms of flexible joints to enable the pipe to conform to the 
grade of the trench, and special joints for easy connection where divers 
are employed. Submerged pipe should be thoroughly tested either in 
sections before laying, or better, after the line is completed, in which 
case compressed air can be used for the purpose. Leakage of air will 
be indicated by the appearance of bubbles, and the imperfect joints can 
then be calked by divers. The various methods of laying submerged 
pipe will now be described together with some of the special details 
used in this work. 

* Proc. Am. W. W. Assn., 1892, p. no. See also description of boxing at 
Duluth, in Eng. Record , 1899, XXXIX. p. 162. 

f Eng. News , 1892, xxvn. p. 424. 





SUBMERGED PIPES. 


567 


1. Where the stream is shallow, a common method of laying is 
first to connect the entire pipe, or large sections of it, on platforms 
extending across the stream, and to lower the portion so connected by 
means of screws. Ordinary joints can usually be employed and the 
pipe put together to fit the profile of the trench. Pipes can very con¬ 
veniently be laid in this way from the ice during winter. 

Two cases of this method of laying will be briefly noted. At Cedar Rapids, 
la., 600 feet of 16-inch pipe was laid in this way in a depth of feet of 
water. A trench 2 feet deep was first excavated, and framed trestle-bents set 
up 12 feet apart. A barge was then run between the legs of the trestles, the 
pipe put together on the barge, and then slung by straps fastened to i^-inch 
threaded rods suspended from the trestles. When the entire pipe-line was 
connected, it was all lowered together, electric-bell signals being used to 
secure simultaneous action among the several men stationed at the screws. 
The cost of laying was $1.25 per foot.* 

At Escanaba, Mich., 2000 feet of 12-inch wrought-iron pipe was lowered 
through ice at a cost of $200. The trench was excavated in sand by means 
of the water-jet, after the pipe was laid.f 

Where the pipe cannot readily be built to conform to the trench, 
or where settlement is feared, a certain number 
of flexible joints may be used. The most com¬ 
mon form is the Ward joint, designed by Mr. 

J. F. Ward many years ago. It is illustrated in 
Fig. 173. To make the joint tight requires that 
some tension be put upon the pipe after the joint 
is in place. Other forms of flexible joints are 
illustrated on page 531. 

2. Instead of connecting the entire pipe-line 
and lowering all together, it may be lowered in 
sections by the aid of flexible joints, each section consisting of several 
lengths of pipe connected in the usual manner. The pipe can thus be 
laid and lowered from a short piece of trestle or from a barge. This 
method is especially suitable for deep water where trestles cannot 
readily be used. 

At Portland, Oregon, a 28-inch cast-iron pipe was laid from barges and 
trestles, the former being used in deep water and the latter in shallow water. 
The pipe was lowered from the barge by sliding it down a cradle extending 
from the barge to the river bottom. Flexible joints were used throughout.! 

At Columbus, Ga., an 18-inch main was laid by the use of twenty-four 
flexible joints. The pipe was put together on shore in 204-foot sections, 



Fig. 173.—Ward Flexi¬ 
ble Joint. 


* Eng. Record , 1898, xxxvil. p. 97. 
f Eng. Record , 1899, XL. p. 72. 

j Trans. Am. Soc. C. E.. 1895, xxxm. p. 257. Several flexible joints are here 
described. 










568 


CONDUITS AND PIPE-LINES. 


each terminating in one-half of a flexible joint. The sections were floated 
into place one by one, connected to the end of the previously laid portion 
and then sunk. All leaky joints were afterwards calked by divers.* 

At Rochester, N. Y., a 6o-inch steel intake-pipe was laid in sections ioo 
feet long, joined by means of flexible joints. The pipe was connected above 
water and lowered joint by joint by means of winches supported on pile plat¬ 
forms. The joint used was similar to that shown in Fig. 174.f 

3. Many lines of submerged pipe have been laid by joining several 
lengths on shore, towing them into position, sinking them and connect¬ 
ing them by divers. This method is especially applicable for large 
pipe-lines. It has been used for large intakes at Syracuse and at 
Milwaukee; also at Galveston, Nashville, Boston, and many other 
places. 

The method of laying the Syracuse intake was as follows: J The 52-inch 
pipe was first riveted together in sections 116 feet long. The ends of these 
sections were then closed with oiled canvas bulkheads, rolled into the water, 
and floated to a position between the sections of a catamaran stationed over 
the pipe-trench and held in place by spud-piles. Ropes were then attached 
to the pipe, the bulkheads removed, and the pipe lowered to rest upon small 
timber foundations secured to the pipe before sinking. The joining was done 
by a diver. The special joint used in connecting the sections is illustrated in 
the right-hand portion of Fig. 174. A cast-iron hub is riveted to the end of 



Fig. 174.—Flexible and Rigid Joints, Syracuse Intake. 

one section, and through this pass twenty hook-bolts. After guiding the pipes 
into place these hooks are brought to bear against a loose hoop of wrought 
iron placed on the end of the other section, and the nuts screwed up, thus 
closing up a lead-pipe gasket and forming a tight joint. Several flexible 
joints were used at changes of grade, and one of these is also illustrated in the 
figure. It is made by joining short pieces of pipe by a very broad lead joint 
run into the space between the two 4-inch channels and a cast-iron spigot. 
A 12-degree deflection is permitted. The cost for the pipe delivered was 




* Eng . Record , 1899, XL. p. 97. 

+ Eng. News, 1895, xxxm. p. 234. 

\ Trans. Am. Soc. C. E.. 1895, xxxiv. p. 23. 
















SUBMERGED PIPES. 



$b.8o per foot, including seven flexible joints. The laying (exclusive of 
trenching) cost $2.50 per foot. 

Similar joints were used on the Duluth intake at a cost of $82.00 each for 
the rigid joints, and $398.25 for the flexible joints. The 60-inch pipe there 
used cost $9.11 per foot delivered. Flexible joints very similar in design 
have also been used at Toronto and at Rochester, N. Y., as already noted. 

The 60-inch cast-iron intake at Milwaukee was laid in 50-foot lengths and 
joined by a diver. The spigot end of each section was fitted with a temporary 
hub and poured with lead before it left shore. After entering it into the hub 
of the previously laid section it was then pulled tight by means of clamps as 
illustrated in Fig. 175. As much as 200 feet of pipe per day was laid by this 
method.* 


/& 



Iron Bond 


„ cefi/ffd 
with Lead 



Fig. 175.— Joint for Cast-iron Intake, 
Milwaukee. 



Fig. 176.— Flexible and Taper Joints, 
Boston. 


In laying submerged pipe under the Charles River, Boston, three types of 
joints were used : (1) the ordinary joint with three turned grooves in the 
bell instead of one; (2) a taper joint for making subaqueous connections; and 
(3) a flexible joint. The last two are illustrated in Fig. 176. In making the 
taper joint the sections are put together, the joint run with lead, then the 
sections drawn apart, leaving the lead in place. A similar form of joint has 
been used in many places. In the flexible joint the spigot is turned to a. 
spherical surface and cut off so as to permit a deflection of 1 in 10 without 
projecting into the waterway. It comes in contact with a rib on the bell 
turned to a close fit. In laying, the pipes were put together on a platform 
on shore in sections of 6 or 7 lengths, then towed in place and sunk. They 
were adjusted according to the direction of a diver, and the sections drawn 
together by a hydraulic cylinder attached to the pipe already laid. The joints 
were calked by the diver. Flexible joints were used where there were 
vertical deflections, or where settlement was to be feared.')' 

4. A method of laying submerged pipes sometimes used is to con¬ 
nect the entire pipe, or sections of it, on shore in a line in the direction 
of the proposed main, and to haul the pipe into the stream by a winch 


* Eng . News , 1895, xxxiv. p. 187. 
f Eng. Record , 1898, xxxvn. p. 518. 
















































570 


CONDUITS AND PIPE-LINES. 


on the opposite side, the pipe being'at the same time floated by lash¬ 
ing it to empty barrels. At the Mersey River crossing of the Liver¬ 
pool line a temporary pipe was laid by riveting up complete a 12-inch 
steel pipe and hauling the entire main across at one operation. 
In this method flexible joints should be used in sufficient number to 
permit of all necessary deflections from a straight line. 

5. Very short crossings of deep channels may often be conveniently 
made by riveting up the pipe and sinking the entire structure at one 
operation. This method avoids obstructing the channel for any 
considerable time, and has been used in the case of several narrow 
navigable streams. 


COST OF AQUEDUCTS AND PIPE-LINES. 


654, Canals and Masonry Aqueducts. —The cost of conduits of this 

class can be quite closely estimated, if constructed in ordinary ground, 
from an itemized estimate of quantities, the unit prices being about the 
same as noted on pages 353 and 387. The unit prices used by Freeman 
in the report already referred to were based on the actual cost of the 
large Wachusett aqueduct of Boston. They were: 


For Aqueditcls in Cnt-and-cover : 

Earth excavation. 

Earth borrow. 

Rock excavation. 

Portland-cement concrete. 

Natural-cement concrete. 

Brick lining. 

For Tunnels : 

Heading excavation. 

Bench excavation. 

Brick lining. 

Brick backing. 

Rubble backing. 

Dry backing. 

Portland-cement concrete in side lining 
Natural-cement concrete in side lining. 


•$0.35 per 
. 0.30 “ 

. 1.50 “ 

. 6.00 “ 

• 5-oo “ 
.13.00 “ 

. 7.00 “ 

. 4.00 “ 
<=13.00 “ 

. 6.50 “ 

. 4.00 “ 

. 2.00 “ 

. 8.00 “ 

• 6.50 “ 


cubic yard. 


4 4 

4 1 

4 4 

4 < 

< ( 

< 4 

a 

<« 

4 i 

t 4 


n 

44 

4 4 

44 

1 4 

44 

4 i 

44 

t 4 

4 4 

i 4 

44 

4 4 

4 4 

4 4 

44 


The Sudbury aqueduct of a cross-section equivalent in area to a 
circle feet in diameter cost $23.86 per foot, excluding special struc¬ 
tures. The Wachusett aqueduct cost about $24.00 per foot. Its 
cross-section is equal to a circle of 11.33 feet m diameter. 

655. Pipe-lines. —The cost of pipe-lines will vary greatly according 
to the cost of the material used. This element can readily be ascer¬ 
tained at any time by reference to current price-lists, and the item of 

















COST OF AQUEDUCTS AND PIPE-LINES. 571 

transportation can also be quite easily determined. For a good 
detailed analysis of amount and cost of labor, reference may be made 
to Weston s “Tables for Estimating the Cost of Laying Cast-iron 
Water-pipe, ’ also to Billing’s “Details of Water-works Construc¬ 
tion, and to contract prices in the current periodicals. The data here 
given are intended only to give a general notion of the relative cost of 
work of this character. The formula already given (page 550) for the 
approximate cost of cast-iron pipe, furnished and laid, is 

c — 20 -f- 2 ad 1 - 5 *, 

where c — cost per foot in cents, a — cost of pipe per pound, d =' 
diameter of pipe in inches. This formula has reference to work done 
under average conditions, and for earth-excavation, and refers only to 
ordinary sizes of pipe. From this formula the cost of various sizes is 
as follows: 


Size of Pipe. 

Cost per Foot. 

Cost of Pipe 
= x cent per lb. 

Cost of Pipe 
= cents per lb. 

/|-i nrh. 

$0.37 

•52 

.70 

.91 

1. 14 

I.67 

2.28 

2.96 

$0.46 

.68 

•95 

1.26 

1.61 

2.40 

3 - 32 

4 - 33 

6- “ . 

8- “ . 

10- “ . 

12- “ . 

l6- “ . 

20- “ . 

24 - “ . 



These figures are not intended to include the items of contractors' 
profit and of engineering. 

The actual cost per foot of pipe, for distributing pipes, valves, etc., 
at Plainfield, N. J., is given as follows:* 



6-in. 

8-in. 

12-in. 

16-in. 

Pipes and specials. 

Lead and yarn . 

Valves and boxes .. 

Tools and labor. 

Contractor and engineering. 

Total. 

$0,394 
.04 
.041 
. 124 
•034 

$0,561 

.050 

.050 

.165 

.063 

$0,965 

.087 

•054 

.177 

.061 

$1,580 

.097 

.072 

.260 

.089 

$0,633 

$0,889 

$ 1-344 

$2,098 


* Trans. Am. Soc. C. E., 1894, xxxi. p. 375. 















































572 


CONDUITS AND PIPE-LINES. 


A similar statement for Alliance, Ohio, shows very nearly the same 
cost.* 

In large cities where pavements are disturbed and the price of 
labor is high, the cost of pipe-laying is likely to be considerably more 
than given above. 

For very large cast-iron pipes the cost of the iron, lead, and trans¬ 
portation forms such a large proportion of the total cost that a relatively 
close estimate can be made when these items are once known. 

Table No. 78, compiled by Adams, + aims to give comparative 
figures for the cost of wood-stave, steel, and cast-iron pipe. The 
figures are based on a cost of cast-iron pipe of $19.00 per ton, and of 
steel of 1.6 cents for No. 14 B. W. G. plate to 1.25 cents for No. 8 
and thicker. These prices are exceptionally low. They are now 
(1901) much higher, and the figures of the table should be correspond¬ 
ingly raised. The costs as given do not include hauling nor con¬ 
tractors’ profits; they are intended to be used for comparative purposes 
only. 

TABLE NO. 78 . 


COMPARATIVE COST OF PIPE AT CHICAGO (ADAMS). 
(Including Laying, but not Hauling.) 




Stave. 


u 

V 

4 -» 

<u 

a 

cd 

5 

T 3 


73 

rd 

73 

cd 

c 3 

c 

cd 

aj 

33 

6 

X 

s 

V 

X 

• — 



4 -» 

4 -> 

a 

0 

£ 

+-» 

V-. 

1 

10 

N 

V-. 

6 

LO 

v_< 

8 

H 

8 

N 

12.. 

.42 

•49 

•63 

•85 

18.. 

.69 

. So 

1.02 

I.46 

24... 

•79 

.91 

I . 14 

1.61 

30.. 

.96 

I . 12 

1.44 

2.06 

36.. 

1.19 

I. 4011.82 

2.65 

42 • • 

1.40 

1.68 

2.23 

3-33 

48.. 

1-55 

1.85 

2.46 

3-67 

54 - • 

2.23 

2.62 

3-43 

5.02 

60.. 

2.85 

3-35 

4-37 

6.40 

66.. 

3.21 

3 . 8 i 

5-oo 

7-38 

72 . . 

3-65 

4-38 

5-83 

8.27 


Steel Riveted. 

Cast Iron. 

d 

6 

d 

d 

d 








£ 

* 

£ 

£ 

£ 




73 

•0 

73 

cd 

73 

cd 

cd 

cd 

c'T 

cd 

0 

PQ 

CQ 


J 3 


cd 

V 

X 

(d 

V 

X 

CD 

X 

<u 

X 


M 

M 

00 

\o 

•G 

u 


• 

• 

+3 


o’ 

fc 

o’ 

o’ 

£ 

o’ 

6 

X 

G 

■R 

c 

1 

C 5|00 

V-i 

10 

Vh 

1 

0 

l 

8 

H 

8 

vN 

•32 

•38 

•44 






.73 

• 77 

.84 

1.00 

• • • • 

•57 

•65 

•78 

.98 




1.29 

i -35 

I.46 

1.70 



•85 

I.04 

1.28 

i -55 

1.99 

• • • • 

1.91 

2.00 

2.18 

2-55 




1.27 

r -59 

i -93 

2.46 

3-04 

2.67 

2.80 

3-°7 

3.61 




i -55 

1-93 

2.30 

2.92 

3-58 

3.47 

3-67 

4.06 

4-85 

• • • • 

• • • • 

• • • • 

1.61 

2.18 

2.66 

3-37 

4.12 

4.42 

4.69 

5.22 

6.28 





2.48 

3-03 

3-83 

4.66 

5.50 

5.84 

6 -53 

7.92 





2.80 

3 - 4 i 

4.29 5.21 

6.65 

7.10 

8.00 

9.78 






3-79 

4-75 

5-74 

8.04 

8.63 

9.80 

12.13 






4-35 

5-21 

6.29 

9 - 5 i 

10.16 

11.55 

14.05 






4-52 

5.66 

6.83 

11.32 

12.00 

13.26 

16.00 


Regarding the actual cost of steel pipe-lines the following data are 
given: 


* Eng. News , 1894, xxxi. p. 490. 
t Trans. Am. Soc. C. E., 1899, xlt. p. 58. 







































































LITER A TURK. 


573 


The Rochester 38-inch steel conduit, 26J miles long, built in 1894, 
cost about $8.10 per foot, ready for use. The pipe was composed of 
J-, -1$-, and f-inch plates with lap-joints. The 40-inch steel pipe for 
Cambridge, Mass., built in 1895, 4.6 miles long, cost $4.81 per foot, 
or 3.13 cents per pound. The pipe thickness was inch, and lap- 
joints were used. The contract price of the Allegheny 60-inch steel 
pipe was about $8. 50 per foot. The plates were f-inch thick. The 
pipe was built: in 1896. Bids for the New Bedford 48-inch steel-pipe 
line in 1896 were, for the pipe alone, $5.10 per foot for lap-joints and 
$5.65 for butt-joints and countersunk rivets. The plates were yL-inch 
thick, and length of line 8 miles. For the conduit complete the corre¬ 
sponding prices were $7.55 and $8.10 respectively. 

Freeman estimates the cost of steel-pipe conduits of f-inch metal 
for New York City as follows: 4-foot pipe, $13.90 per foot; 5-foot pipe, 
$16.70; 6-foot pipe, $19.50; 7-foot pipe, $22.50, etc.* These prices 
cover conduit complete, made with butt-joints and countersunk rivets, 
specially well coated, 10 per cent of length of trench in rock ledge, 
and assumes cost of steel at 2f cents per pound. 


LITERATURE. 

CANALS AND MASONRY AQUEDUCTS. 

1. Fteley. Stability of Brick Conduits. Jour. Assn. Eng. Soc., 1883, 11. 

p. 123. 

2. FitzGerald. Aqueducts on High Embankments. Eng. News, 1884, xi. 

p. 212. 

3. The New Croton Aqueduct is described in detail in the Report to the 

Aqueduct Commissioners of the President, Secretary, and Chief 
Engineer, 1887-95. Also in Wegmann’s “Water-supply of New 
York,” 1896, and in various volumes of the Eng . News and Eng. 
Record , particularly those of 1884 and 1885. 
a 0 Carter. Farm Pond Aqueduct, Boston, Mass. Jour. Assn. Eng. Soc., 
1889, viii. p. 73. Construction through soft material. 

5. Chenoweth. The New York City Aqueduct; its Engineering Features 

and Design. Jour. Frank. Inst., 1890, cxxix. p. 135. 

6. The Brooklyn Water-works Extension. Eng. News , 1891, xxv. p. 225. 

7. The Manchester Water-works. Engineering , 1891, lii. p. 435 - Also 

Proc. Inst. C. E., 1896, cxxvi. p. 2. 

8. FitzGerald. Lining a Water-works Tunnel with Concrete. Trans. Am. 

Soc. C. E., 1894, xxxi. p. 294. 

9. Hall. The Santa Ana Canal of the Bear Valley Irrigation Company. 

Trans. Am. Soc. C. E., 1895, xxxm. p. 61. 

10. The New Croton Aqueduct and Storage System. Eng. Record , 1895, 
xxxii. p. 223. 


* Report on New York’s Water-supply, 1900, p. 328. 





574 


CONDUITS AND PIPE-LINES. 


11. The Wachusett Aqueduct of the Boston Water-works is fully described 

in the Annual Reports of the Metropolitan Water Board, 1896-99. 
Detailed descriptions are also published in Eng. News , 1896, xxxv. 
p. 53; 1897, xxxvii. p. 114; and in Eng. Record, 1898, xxxvm. 
p. 405. 

12. Landis. The Croton Aqueduct Embankment. Eng. News, 1897, 

xxxvm. p. 164. Embankments of old aqueduct illustrated. 

13. Report on the Advisability of Completing the Abandoned Aqueduct 

Tunnel, Washington, D. C. Etig. News, 1896, xxxv. p. 125. 

14. Completing the Abandoned Aqueduct Tunnel at Washington, D.C. 

Eng. News , 1899, xlii. p. 410. 

15. Hutton. The Washington Aqueduct, 1853-98. E?ig. Record, 1899,. 

xl. p. 190. 

16. Freeman. Report on New York’s Water-supply, 1900. Contains much 

valuable information on the construction of large aqueducts. 


PIPE-LINES. 

1. Construction of the East Jersey Water Company’s Aqueduct and Reser¬ 

voir. Eng. Record, 1891, xxiv. p. 139. 

2. Gutelius. Construction of the Wooden Pipe-line for Butte City Water¬ 

works. Jour. Assn. Eng. Soc., 1893, xn. p. 209. 

3. Herschel. The Works of the East Jersey Water Company for the Supply 

of Newark, N. J. Jour, New Eng. W. W. Assn., 1893, vm. p. 18; 
Eng. News, 1893, xxix. p. 559. 

4. Schuyler. The Water-works of Denver, Colo. Trans. Am. Soc. C. E.,. 

1894, xxxi. p. 135. 

5. Hall. The Santa Ana Canal of the Bear Valley Irrigation Co. Trans. 

Am. Soc. C. E., 1895, xxxiii. p. 61, 

6. The New Steel and Masonry Water-supply Conduit, Rochester, N. Y. 

Eng. News, 1895, xxxiii. p. 234; Eng. Record, 1895, xxxi. p. 346 
et seq. 

7. Hill. The Water-works of Syracuse. Trans. Am. Soc. C. E., 1895, 

xxxv. p. 23. 30-inch cast-iron conduit. 

8. Payson Park Reservoir, Cambridge, Mass. Eng. Record, 1895, xxxiv. 

p. 25. Steel pipe-line described. 

9. Sixty-inch Steel Conduit for the Water-works of Allegheny, Pa. Eng . 

News, 1895, xxxiv. p. 234. 

10. Tuttle. The Economic Velocity of Transmission of Water through 

Pipes. Eng. Record, 1895, xxxn. p. 258. 

11. Adams. The Astoria City Water-works. Trans. Am. Soc. C. E., 1896, 

xxxvi, p. 1. Steel and wood-stave conduit. 

12. Hill. The Thilmere Works for the Water-supply of Manchester. Proc. 

Inst. C. E., 1896, cxxvi. p. 2. 

13. Deacon. The Vyrnwy Works for the Water-supply of Liverpool. Proc. 

Inst. C. E., 1896, cxxvi. p. 24. 

14. Goldmark. The Power-plant, Pipe-line, and Dam of the Pioneer Elec¬ 

tric Power Company at Ogden, Utah. Trans. Am. Soc. C. E., 
1897, xxxvm. p. 246. Steel and wooden pipe-line. 

15. Wood. The Further Water-supply of the City of New Bedford. Jour. 

New Eng. W. W. Assn , 1897, xi p. 202. Steel pipe-line. 


LI TER A TURK. 


575 . 


16. The Sewage Farm of Acheres, Paris. Annales des Ponts et Chaussees, 

1897, 11. p. 1. Abstract, Eng. News, 1898, xxxix. p. 170. Cement- 
and-steel pipe-lines. 

17. Bailey. I he Design of Force-mains. Eng. Record , 1898, xxxvii. 

p. 254. 

18. The Coolgardie Pipe-line. Eng. News, 1898, xl. pp. 233, 423; Eng. 

Record, 1900, xli. p. 178. A pipe-line 328 miles long. 

19. Some Notable Australian Steel Pipe-lines. Eng. News, 1899, xli. 

p. 406. 

Submerged Pipes. 

(See also literature of Chapter XIII.) 

1. Dechant. Submerged Pipe-laying for the Pennsylvania Sanitary Sewage 

Company, at Reading, Pa. Proc. Fng. Club, Phila., 1895, xn. 

P- 243* 

2. Riffle. A Line of 28-inch Cast-iron Submerged Pipes across the Wil¬ 

lamette River at Portland, Ore. Trans. Am. Soc. C. E., 1895, 
xxxiii. p. 257. 

3. Laying Submerged Water-mains, Cedar Rapids, la. Eng. Record, 1898, 

xxxvii. p. 97. 

4. A Submerged Water-main Tunnel, Cleveland, 0 . Eng. Record, 1898, 

xxxviii. p. 449. 

5. Subaqueous Pipe-laying, Boston, Mass. Eng. Record, 1898, xxxvii, 

p. 518. 

6. Laying a Submerged Water-main at Cleveland, 0 . Eng. Record , 1898, 

xxxvii. p. 187. 

7. Laying Submerged Pipes. Eng. Record, 1899, xl. pp. 72, 96. 


1 




CHAPTER XXVI. 


PUMPING-MACHINERY. 

656. Introductory. —The cost of pumping water is usually the 
greatest operating expense of a water-works system, and a city which 
can secure an adequate gravity supply has at once eliminated a most 
expensive and troublesome feature from the system. Pipe-lines, reser¬ 
voirs, dams, and like structures, if well designed and properly con¬ 
structed, are permanent and require but little attention and entail little 
expense for maintenance. All operating mechanisms, of whatever 
kind, require more or less constant attention and, however well designed 
and constructed, must, of necessity, be subjected to more or less wear 
and possible disarrangement and breakage. 

The best results of intellect are secured by concentrated rather than 
by continuous effort. Proper consideration and supervision will secure 
well-designed and well-constructed works, but no care in the original 
design or in the construction will assure intelligent operation. In the 
course of time, intelligently designed works may come into the hands 
of unintelligent operatives and poor results follow. Poor designs, poor 
construction, and poor operation frequently entail large and unneces¬ 
sary expense in the operation of pumping-plants. 

Where water cannot be obtained at an elevation sufficient to admit 
of satisfactory gravity pressure at the points where it is to be used, 
pumping-machinery becomes necessary. It then becomes the duty of 
the engineer to design a pumping-plant which shall be the most 
economical for the condition under which the plant is to be established 
and operated. 

This design involves the selection of— 

1st. The best source of energy available for power purposes; 

2d. The best means of generating such energy from a potential 
form, and for converting it into a form in which it can be utilized for 
power; 

3d. The most economical means of transmission of the power so 
developed from the point of generation to the point of application; and 

576 


ENERGY EXPENDED IN PUMPING WATER. 577 


4th. The form of pump best adapted for the conditions under which 
it is to be operated. 

These factors are often largely modified by the nature of the source 
of water-supply, and by various other features of a water-works system. 
All of these must be considered in connection with the selection of the 
pumping-plant, for many of them exert an important influence on the 
conditions under which the plant must be operated, and, therefore, 
often determine the type of the plant available for any particular pur¬ 
pose. (See Art. 688.) 

In the generation, conversion, transmission, and application of 
power to pumping purposes, there are many losses of energy which add 
greatly to the expense of pumping. Many of these cannot be obviated; 
others can be removed, or at least reduced, by careful design. Care¬ 
ful analysis of each detail of the plant will determine the points at which 
a saving may be effected and will enable the engineer to reduce these 
losses to a minimum. 

It is the purpose of this chapter to furnish an outline of the points 
to be examined in making such an investigation, and the methods to 
be used and factors to be considered in the selection of pumping- 
machinery; also, to describe briefly the various types of pumping- 
machinery which may be utilized, and their adaptability to different 
conditions. 

657. Energy Expended in Pumping Water. — An expenditure of 
energy is entailed whenever motion is transmitted to a body. A por¬ 
tion of this energy is used in producing the velocity, a portion in over¬ 
coming frictional resistances (“lost” work), and a portion in over¬ 
coming other resistances involved in doing “useful” work, such as 
raising a body to a higher elevation, etc. 

In hydraulic problems the energy expended in producing velocity 
may be readily transformed to pressure-energy by the familiar expres¬ 
sion 



in which h = pressure-head, 
v — velocity, 

g = acceleration of gravity. 

If q — volume of water moved, and w = weight of a unit of volume, 
then the work performed in producing the velocity v will be 


ir 


work = = qwh . 



578 P UMPING-MA CHINER V. 

Thus if q ^ io gallons, w — pounds, v = 4 feet per second, the 

4 2 

work will be equal to 10 X H X — = 20.69 foot-pounds. If 10 

gallons of water is moved each second, then the rate of work is 20.69- 
foot-pounds per second = .37 H.P. 

The greatest expenditure of energy, however, is usually incurred 
in overcoming the resistance, or pressure, against which the motion is 
produced. 

If h x — the feet in height to which water is raised, then the useful 
work performed will be: Work (in foot-pounds) = qwh v 

If h x — 100 feet, q = 10 gallons per second, w = 8J- pounds, then 

Rate of work = qwh — 8330 foot-pounds per second = 15.14 H.P. 

Again, if h 2 = the friction-head, the work lost in friction will be, in 
foot-pounds, equal to qwh ¥ 

If h 2 = 5, with q and w as above, then the work lost to overcome 
friction will equal 416.5 foot-pounds per second, or about .75 H.P., 
and the total work done by the pump will be 

Work (in foot-pounds) = qw(Ji -f- /q -f- /q). 

In pumping water the largest expenditure should be and usually 
is due (except in the case of very long pipe-lines) to overcoming 
the resistance of gravity, or in useful work, although the energy used 
in acquiring velocity and in overcoming the frictional resistance of 
passages and conduits through which water passes may be considerable, 
especially in poorly designed machinery or ill-devised pipe systems. 

In overcoming gravity or other resistance, the quantity of water 
raised and the resistance overcome are the measures of energy 
expended. In certain cases the energy used in producing velocity may 
be returned in work done without loss. In other cases such energy 
cannot be utilized. 

Table No. 79 shows the equivalence of various units of quantity, 

TABLE NO. 79 . 


EQUIVALENT MEASURES AND WEIGHTS OF WATER AT 4° CENT. = 39-2° FAHR. 


U. S. Gallons. 

Cubic Feet. 

Cubic Inches. 

Imperial 

Gallons. 

Liters. 

Cubic Meters 

Pounds. 

I 

•I 33 68 

231 

•83321 

3.7853 

•OO37853 

8.34112 

7-48055 

I 

1728 

6.23287 

28.3161 

.0283161 

62.3961 

.CO4329 

.OOO579 

I 

.003607 

.016387 

.OOOO164 

.03611 

I.20017 

.160439 

277.274 . 

I 

4.54303 

.0045303 

IO.OIOS 

.264179 

.035316 

6l.0254 

.22012 

I 

.OOI 

2.20355 

264.179 

35 - 3^63 

61025.4 

220.117 

IOOO 

I 

2203.55 

.119888 

.016027 

27.694 

.099892 

•453813 

.0004538 

I 






















'yVOKK A.YD POWER EQUIVALENTS . 


579 


and Table No. 80 shows the equivalence of various pressure 

TABLE NO. 80 . 

PRESSURE EQUIVALENTS. 


Feet 

Head. 

Pounds 
per Sq. In. 

Pounds 
per Sq. Foot. 

Pounds 
per Circular 
Inch. 

Inches of 
Mercury, 

32 0 Fahr. 

Kilograms 
per Sq. Centi¬ 
meter. 

Atmosphere. 

I 

•4335 

62.425 

.3413 

.882 

-03047 

•02945 

2.307 

1 

144 

.7854 

2.0379 

.07029 

.06794 

.01602 

.006939 

I 

.OO545 

.01414 

.000487 

.00047 

2-937 

1-273 

I 83-3 

I 

2-594 

.08952 

.08649 

i -133 

.4912 

70.73 

, .3858 

1 

•03453 

•03334 

32.821 

14.225 

2047.8 

Ii.174 

28.992 

I 

.96652 

33-95 

14.72 

2IT9.7 

II .562 

29.921 

1.035 

I 


resistances, which, in any particular case, may be due to gravity or to 
other causes, such as the resistance of the spring of a relief-valve, or 
the friction through pipe, hose, nozzle, etc. In pumping water these 
two tables include the elements of the useful work done. 

658. Work and Power Equivalents. —Work is a phenomenon of 
energy; it is the overcoming of a resistance b}' a force acting through 
space. Power is the rate of work and involves the idea of force, space, 
and time. 

In pumping water any form of energy may produce a force which, 
when properly applied, will overcome a given resistance, such as a 
given head or pressure. In doing this, work is performed. If a 
definite weight or quantity of water is pumped against a definite head 
or pressure in a given time, certain work is done each unit of 
time. Thus a rate of work is established and certain power is 
expended. Both work and power in pumping are therefore measured 
by the quantity of water pumped and the resistance pumped against. 
For considering power, the second, minute, hour, or day are the units 
of time used. 

Table No. 81 gives the equivalence of units of energy or work, i.e., 
the idea of time is not involved. 

Besides the units of work given in Table No. 81 the various power- 
units, when limited to a definite time, may also be used to designate a 
definite amount of work, in which the unit of time is used to limit the 
quantity of work to be performed, but does not necessarily involve the 
idea of the time in which the said work is performed. Various fuels and 
other forms of potential energy may also be expressed directly in foot¬ 
pounds. Table No. 82 shows the relation or equivalence of such units 

in foot-pounds. 

















580 


PUMPING-MA CHI NEK Y. 


TABLE NO. 81. 

EQUIVALENT UNITS OF ENERGY. 


Work. 

Heat, B.T.U. 

Electricity. 

Hydraulic Energy. 

Foot- 

Degree- 

Volt- 

Foot- 

Foot- 

Pound- 

Pound- 

pounds. 

pounds. 

coulombs. 

gallons. 

cubic-feet. 

gallons. 

cubic feet. 

I 

.001285 

.OOO3766 

. 12 

.0l6 

.0519 

.0069 

778 

I 

. 2929 

93-28 

12.448 

40.394 

5.368 

2655-4 

3-414 

I 

318.39 

42.486 

I 37-87 

183.23 

8.341 

.01072 

.003140 

I 

-1334 

•433 

-05754 

62.39 

.08033 

.02353 

7-48 ^ 

I 

3-245 

.4312 

19-259 

.02476 

.007255 

2.309 

.30816 

1 

.1329 

144.92 

.1S630 

•05457 

17-37 

2.318 

7-524 

I 


TABLE NO. 82. 


WORK EQUIVALENTS. 


Unit. 

Horse-power hour. 

Kilo-watt hour. 

Pound of steam (approximate). 

British thermal unit. 

Pound of carbon (approximate). 

Pound of hard coal (approximate).. 
Pound of soft coal (approximate)... 
1,000,000 gallons 1 foot high (water) 
1000 gallons 100 feet high (water)... 
100 cubic feet 1 foot high (water).. . 


Equivalent in Foot-pounds. 

. 1,980,000 

. 2,654,150 

. 778,000 

. 778 

. 11,500,000 

. 11,400,000 

. 9,910,000 

8,341,000 

. 834,100 

. 62.396 


In many problems of pumping, questions of power, rather than 
work, are involved. That is, a definite rate of pumping must be con¬ 
sidered. Table No. 83 gives the equivalence of common power units 
used for such problems. 


TABLE NO. 83. 


EQUIVALENT UNITS OF POWER. 


Work. 

Heat. 

Electricity. 


Water- 

power. 




Thermal 


Foot- 




Foot-lbs. 

Horse- 

Units 

Watts. 

Foot- 

Pound- 

Pound 

per Minute. 

power. 

per Minute, 
B.T.U. 

gallons 
per Minute. 

cubic-feet 
per Minute. 

gallons, 
per Minute, 

cubic-feet, 
per Minute. 

I 

.OOOO303 

.001285 

.0226 

.12 

.016 

.0519 

.0069 

33,000 

I 

42.416 

746 

3960 

528 

1713.4 

229.05 

778 

.02357 

I 

17-58 

93.28 

12.444 

40.394 

5.388 

44.24 

.OOI34 

.0568 

I 

5.308 

•70895 

2.296 

•307 

8-34 

.00025 

.0107 

.18856 

I 

•1337 

-433 

•0579 

62.396 

.00189 

.0802 

I.4105 

7.48 

I 

3-24 

•433 

19.26 

.00058 

.0247 

•435 

2.31 

•309 

1 

• 1337 

144.92 

.00436 

. 1851 

.0326 

17-37 

2.31 

7.48 

1 



























































SO URGES OF POTENTIAL ENERGY. 


5 8l 


659. Classification of Energy Losses.—If it were possible to perform 
work or to utilize power without loss, the amount of energy which 
would be necessary to raise any given quantity of water in any given 
case could be ascertained from the preceding tables. Energy loss is, 
however, concomitant with the use of all machinery, and differs with 
the class and complication of the machinery through or in which the 
energy is generated, transformed, transmitted, and utilized. 

In general the operation of applying energy to pumping water con¬ 
sists of the generation of energy from a potential source, the conversion 


TABLE NO. 84. 


CLASSIFICATION OF ENERGY LOSSES IN PUMPING. 


£ 

O 

r 1 

< 

W 

Z 

w 

O 


z 

c 

C/1 

oi 

w 

> 

z 

o 

u 


Fuel. 


' Internal-combustion engine. 
(Gas; Oil.) 


Steam 


l 


Direct (ram). 


f Dire 

1 Water-power. \ 

l Indirect (wheels). 


Electric (primary batteries). 
Wind (mills). 

Waves (motors). 

Sun heat (solar engines). 
Internal-combustion Engine. 


Minor sources. 


Steam .... 
Electrical. 


Hydraulic. 

Pneumatic. 

( ( Direct-connected shaft. 

1 Mechanical. \ Belt; Rope; Chain; 

Combination. 


Losses. 

Engine losses. 

Furnace. 

Boiler. 

Piping. 

Ram losses, 
j Velocity losses. 

/ Wheel losses. 

Various mechanical and 
other losses due to 
method used. 

Included in engine losses. 
Engine and connection 
losses. 

Dynamo losses. 

Pump losses. 

Compressor losses. 




z 

o 

>—I 

c n 
in 
►—« 

2 1 

C/2 

z 
< 


H 


Hydraulic. 

Electrical. 




Pneumatic. 


z 

o 

p 

< I 

HI 


Pumping. 


Inlet-pipe. 


Pump. 

Discharge-pipe. 


Ram.. 
Steam 
Air... 


Various losses, due to the 
T method used. 

( Pipe friction. 

-I Motor losses. 

Connections. 

Transformer losses. 

Wire losses. 

Motor losses. 

Connections. 

Pipe friction. 

Air cooling. 

''i Motor losses, 
f Connections. 

Influx. 

Velocity. 

Friction. 

Friction in valves and 
water passages. 
Mechanical friction. 

Pipe friction. 

Pipe losses. 

Radiation. 

Condensation. 

Pipe losses. 

Air-pipe losses. 






































PUMPING-MA CHJNER Y. 


582 

of such energy into a kinetic form, its transmission to the location of 
the pump, and its application to pumping the water by means of the 
pumping machinery used. 

The economical application of pumping-machinery depends on the 
reduction of all energy losses to the lowest practical amount. These 
losses should always be examined in detail, and in order that they shall 
in no case be overlooked it is well to examine the losses under the 
following heads: 

Generation Losses. 

Conversion Losses. 

Transmission Losses. 

Application Losses. 

These principal divisions should be further subdivided for detailed 
consideration as shown in Table No. 84, the items of which will next 
be considered. 

SOURCES OF POTENTIAL ENERGY. 

660. Available Sources.—The sources of potential energy available 
for power purposes are fuel, water-power, wind, solar energy, and 
chemical energy (which properly also includes the energy of fuel which 
is rendered kinetic through chemical union). Fuel is most generally 
utilized by means of heat and heat-engines, water-power by means of 
various forms of water-motors, the wind by means of windmills, 

TABLE NO. 85. 

FUELS : CALORIFIC VALUE AND EQUIVALENTS. 


Fuel. 

Average Heat-units. 

Per Pound. 

Per 1000 
Cubic Feet. 

Equivalents for Calculations 
r nlfp . .. 

10,000 

14,880 

14,660 

12,740 

7,740 

I 9 U 50 



Anthracite rnal. 


Ritiiminnus roa 1 .. . . . 


W n n d.. . 


^ Pptrolpn m. 


Natural eras... 

885,880 

570,900 

253 UOO 

111,190 

100,000 

Una 1 - era s. 


W a f e r-cra s. 


Prod nrpr-fras. 


Equivalents for Calculations 




Equivalent 
Evaporation 
from and at 
212 0 Fahr. 
Pounds. 

Equivalent 

Horse-power 

Hours. 

Equivalent 

Million 

Foot-gallons. 

10.35 

3-87 

.921 

15.40 

5.84 

I.384 

15.17 

5-76 

I .365 

I 3 .I 8 

5-00 

I.185 

8.01 

3-04 

. 720 

19.82 

7-52 

1.782 

917.06 

348.08 

82.494 

599 93 

224.32 

53.164 

262.00 

99-45 

23.569 

115-10 

43-69 

10-354 

103.50 

38.90 

9.219 


* Gasoline, the form of petroleum used in the gasoline engine, weighs about 5.8 
lbs. to the gallon. Each gallon contains about 110,000 B. T. U. 








































GENERATION AND CONVERSION OF ENERGY. 583 

chemical energy by means of electric batteries, and solar energy by 
means of solar engines. In a commercial way, fuel and water-power 
only are of great importance or need to be here considered. 

661. Fuel. —Fuel is the source of potential energy most widely used 
commercially. From wood, coal, petroleum, natural gas, and other 
fuels, energy is developed in the form of heat by combustion. 

The average value of various fuels is approximately as shown in 
Table No. 85. 

662. Water-power. —Water-power is readily convertible by easy 
calculations into water pumped. Without loss, 1 foot-pound of water 
for power purposes should give 1 foot-pound of water pumped. For 
example, 10 pounds of water falling 10 feet possess 100 pounds of 
energy and would, if utilized without loss, raise 1 pound of water 100 
feet, 2 pounds 50 feet, 4 pounds 25 feet, etc. 

If utilized without loss, we have said; but it has already been stated 
that utilization of energy without loss is impossible*, hence the above 
proportions of work done are in practice materially reduced. 

GENERATION AND CONVERSION OF ENERGY. 

663. Ordinary Efficiency of Generators and Motors —The proportion 
of energy which can be realized in useful work will depend on the 
efficiency of the machines by means of which energy is being utilized. 
By efficiency is meant the ratio of energy utilized in useful work done 
to energy applied for power purposes. 

Any prime mover may be utilized by proper connection with a suit¬ 
able pump for the purpose of pumping water; The loss of energy in 
any case will depend both on the type of machine used and the design, 
construction, and operation of the particular machine in question. 
The results usually attained in good practice with various generators 
and motors which may be utilized for pumping are shown in Table 
No. 86. 

664. The Steam-boiler. —Fuel energy is most commonl)' converted 
into a form in which it can be applied for power purposes by means of 
the steam-boiler, although the internal-combustion engine has also now 
become an important factor for power installations. 

On account of heat lost in the waste gases from the boiler-furnace, 
only about 83 per cent of the calorific value of the fuel can theoretically 
be made available without the use of economizers and forced draft. 
The best boilers will utilize about 90 per cent of this available energy, 
or about 75 per cent of the full calorific power of the fuel used. 




584 P UMPING-MA CHINEE Y. 

TABLE NO. 86. 

ORDINARY EFFICIENCIES OF GENERATORS AND MOTORS. 


Type of Machine. 


Boilers. 


Water-wheels: 

Overshot wheels. 

Breast wheel. ... 

Undershot wheel. 

Turbines.. 

Impulse-wheel... 

Steam generators: 

Steam-engines: 

Triple-expansion Corliss. 

~ , . Compound Corliss. 

Condensing.... < K ~ .. 

& j Simple Corliss. 

[ Compound high-speed .. . 

f Compound Corliss. 

j Simple Corliss. 

Non-condensing^ Compound high-speed... 

| Simple high speed. 

[Simple slide-valve. 

Heat engines: 

Gas- or oil-engines. 

Diesel motor. 

Steam air-compressors: 

Compound condensing Corliss. 

Simple condensing Corliss. 

Simple Corliss. 

High-pressure. 

Small straight-line. 

Electrical machinery : 

Dynamos.... . 

Motor (large). 

Motor (small). 

Transformer. 


Ordinary Efficiency at 
Full Load. 

Minimum. 

Maximum. 

65 

75 

60 

65 

25 

40 

60 

85 

75 

85 

50 

75 

15 

18 

12 

15 

10 

12 

10 

12 

10 

12 

7 

9 

7 

9 

6 

7 

5 

7 

16 

20 

25 

30 

10 

12 

7 

9 

5 

6 

3 

4-5 

2 

3 

80 

92 

80 

90 

75 

85 

50 

95 


The greatest care is necessary in the design and construction of 
furnace, boiler, and accessories in order to develop the maximum 
efficiency and secure the most economical results in the utilization of 
fuels. Radiation and condensation are important factors in boiler 
losses and should be rendered as small as possible by properly protect¬ 
ing the boiler. The same losses are also important in the steam-pipes 
which transmit the steam from generator to motor and must be kept at 
a minimum by proper precautions. 

665. The Steam-engine.—Of the energy delivered to the engine, the 
proportion actually utilized depends upon the character of the engine 
used, its design, and the condition in which it is maintained. 

A perfect engine, on account of the nature of steam, could utilize 
only about 25 per cent of the energy of the steam delivered to it. In 






































THE STEAM-ENGINE. 


585 


actual practice, however, the best engines utilize only about 17 per 
cent, and poor engines in poor condition frequently utilize less than 
1 per cent of the energy of the steam. 

If the steam-consumption per actual horse-power per hour for any 
engine is known, the efficiency of the engine can be readily determined 
from Table No. 82. 

666 . Use of Steam Expansively .—In the simplest form of steam- 
engines and of steam-pumps, the steam at full pressure follows the 
piston for the full length of every stroke and the expansive force of the 
steam is not utilized. This is the case in direct-acting, reciprocating, 
high-pressure steam-pumps. In higher types of steam-pumps and in 
almost all types of steam-engines the steam is cut off after a portion of 
the stroke is completed, and the steam is allowed to expand for the 
balance of the stroke. 

In Fig. 177 let ab represent the pressure on the steam-piston, and 


b b 



aa' the space passed through by the piston; then their product, repre¬ 
sented by area abb'a', equals the work done by a unit of steam with 
pressure ab , and which follows the piston for a space aa'. Now if at 
a’b' the steam-supply is cut off and the piston still advances to position 
a’b" or a"’b '", etc., the expansive force of the steam will still cause a 
pressure to be exerted against the piston which will decrease in amount 
as the piston advances, but which is nevertheless adding constantly 
to the work done, as shown by the area which represents in the 
diagram the work of a unit of steam. This additional work is obtained, 
it should be noted, with no additional expenditure of steam. The 






$86 


PUMPING-MA CHINER Y. 


additional work done by each steam-unit depends on the degree of 
expansion obtained, which in turns depends on the type of engine or 
pump used, and various other considerations which cannot be discussed 
here. 

From Fig. 177 it is seen that if the steam is allowed to expand and 
the pistons to increase its stroke, the power obtained will be increased. 
The power obtained from a cylinder of given size will, however, be 
greater when the steam is carried for the full length of the stroke. 

When the steam-supply is cut off at a fraction of the stroke and 
allowed to expand for the remainder of the distance, the average or 
mean effective pressure (M.E.P.) decreases and the horse-power of the 
engine will likewise decrease unless the pressure of the steam is 
increased sufficiently to offset the loss in M.E.P. thus occasioned. In 
Table No, 87 is shown the initial pressure (column 3) needed to main¬ 
tain a M.E.P. of 75 pounds, or, in other words, the necessary initial 
pressure needed with various cut-offs to obtain the same horse-power 
from the same size steam-cylinder. 

TABLE NO. 87. 


ECONOMY SECURED BY USING STEAM EXPANSIVELY. 


Point of 
Cut-off. 

Boiler-pressure required to give Same 
Power of Engine. 

Per Cent of 
Saving in 
Fuel. 

When Used 
Full Stroke. 

When Cut 
Off. 

Ratio. 

I 

75 

75 

I 

O 


75 

76 

I .OI 

12 

f 

75 

77 

I.03 

22 

1 

75 

82 

I.09 

32 

I 

75 

88.5 

I. l8 

41 

I 

75 

99 

1.32 

50 

i 

75 

125.5 

I.67 

58 

i 

75 

195 

2.60 

68 


From this it is seen that high rates of expansion require either high 
initial steam-pressure or large engines. And the limit is soon reached 
at which the economy of a greater degree of expansion is offset by the 
extra cost of the engine necessary to obtain it. Cylinder condensation 
and various questions of construction also enter into the question and 
become important factors. 

The relative theoretical saving effected by different degrees of 
expansion are shown in the fifth column of Table No. 87. 

667. Use of Condensers .—If the steam, after being used in the 
engine or pump-cylinder, is exhausted into the atmosphere, the piston 


















THE STEAM-ENGINE . 


587 


will work against a back pressure equal to atmospheric pressure (about 
14.7 pounds) plus the iriction in exhaust-passages (usually from 2 to 3 
pounds). If the exhaust passes into a condenser, the back pressure is 
relieved in proportion to the vacuum carried. 

Usually a condenser will add about 10 pounds to the mean effective 
pressure in the engine-cylinder. The percentage of saving by it will 
be the ratio of pressure added to mean effective pressure which would 
otherwise be developed in the cylinder, or 

10 

^ g p = percentage saved. 

Dr. C. E. Emery* gives Table No. 88, showing the estimated 

TABLE NO. 88. 

PERCENTAGE OF GAIN BY USE OF CONDENSER. 



Pounds Steam per Indicated H.P. per Hour. 


Type of Engine. 

Non-condensing. 

Condensing. 

Per Cent 
Gained. 


Probable 

Limits. 

Assumed for 
Comparison. 

Probable 

Limits. 

Assumed for 
Comparison. 

Simple high-speed. 

35 to 26 


25 to 19 

22 

33 

Simple low-speed. 

32 to 24 

29 

24 to 18 

20 

3 i 

Compound high-speed. 

30 to 22 

26 

24 to 16 

20 

23 

Triple high-speed. 

27 to 21 

24 

23 to 14 

17 

29 


steam consumption of various engines and the saving effected by the 
use of condensers. 

668 . Average Steam Consumption. —The approximate average 
steam consumption per indicated horse-power for various classes of 
engines is shown in Table No. 89. 

TABLE NO. 89 . 

APPROXIMATE STEAM CONSUMPTION PER I.H.P. OF VARIOUS TYPES OF STEAM-ENGINES. 
Pound of Steam per Indicated Horse-power per Hour at Full Load. 


Triple-expansion condensing Corliss. 12 to 14 pounds. 

Compound condensing Corliss. 14 to 18 

Simple condensing Corliss. 18 to 21 

Compound Corliss. .„• • • 18 to 21 

Compound condensing automatic. 20 to 24 

Simple Corliss. 24 to 30 

Simple high-speed. 3 ° to 36 

Simple slide-valve. 33 t° 45 


* Trans. Am. Inst. E. E., March, 1893. 


































588 


P UMPING-MA CHINER Y. 


669. Effect of Operating at Partial Load .—From 6 to 1 5 per cent 
of the indicated horse-power of an engine is lost in friction in well- 
designed engines at full load. At partial load the percentage of loss 
is much greater. 

All machinery gives its greatest efficiency when operated at or near 
its maximum capacity. This is due to the fact that the friction of most 
machinery is practically constant at all loads, or nearly so. With a 
100 horse-power engine the friction of the engine will be perhaps about 
10 horse-power, hence the following condition will result: 


Useful Load. 

With no load. 
With 10 H.P. 
With 30 H.P. 
With 70 H.P. 
With 100 H.P 


Friction Load. 

10 H.P. 

10 H.P. 

10 H.P. 

10 H.P. 

10 H.P. 


Mechanical 

Efficiency. 

O <f 0 

50 fo 

7 Si 
3 7 \i 
91% 



Fig. 178.—Steam Consumption for Various Classes of Engines. 


The steam consumption of 'various classes of engines at various 
loads is well illustrated by the diagram of Fig. 178, modified slightly 
from a table by Prof. R. C. Carpenter. 


























































































































HE A T-ENG1NES. 


589 


670. Heat-engines. —Only about 12 per cent of the fuel energy is 
utilized in the indicated horse-power of the best steam-engines, while 
in ordinary practice only from 1 to 3 per cent is so utilized. As the 
loss is largely due to the nature of steam, it has resulted in attracting 
the attention of inventors to other forms of heat-engines for power pur¬ 
poses. The best-known forms of these are the various gas- and 
gasoline-engines in which a mixture of air and gas or vapor is ignited 
or exploded in the engine-cylinder itself, without the interposition of a 
boiler. These engines utilize from 16 to 20 per cent of the calorific 
value of the fuel used, and in some special forms 30 per cent has been 
utilized. These engines are also available for power without the slow 
process of getting up steam, an important matter in operating pump- 
ing-plants for fire service. Another favorable condition is the small 
amount of attention necessary in their operation. 

The availability of this class of motors in entirely a matter of con¬ 
dition, which may be adverse or favorable in any locality or for any 



Fig. 17Q.—Gasoline Pumping-pi.ant, Dundee, Illinois. 


purpose. Fig. 179 shows one of two gasoline-engines with direct- 
connected pumps installed in the water-works at Dundee, Ill. 

While these engines require but comparatively little attention, they 
must have such attention, and the expense of this must not be under¬ 
estimated. Where other work can be done by the engineer, only a, 
portion of his time need be charged to the operation of the plant, but 
where no such work is possible his entire time must be considered. 






590 


PUMPING-MA CHI NEK Y. 


The average amount of fuel required by these engines at full load is 
about as follows: 

Gas-engines: i 2 to 1 5 cu.ft. of natural gas per actual H.P. per hour. 

18 to 22 cu. ft. of coal-gas per actual H.P. per hour. 
Gasoline-engines: . 11 to .14 gal. of gasoline per actual H.P. per hour. 

The makers of high-grade gas-engines will guarantee to develop 
an actual horse-power hour on 12,600 B.T.U. 

TRANSMISSION OF ENERGY. 

Having developed the power at the shaft of the engine or water¬ 
wheel, it must next be transmitted to the pump. This operation also 
involves some waste of energy. 

671. Methods of Transmission and Approximate Efficiencies. —Direct 
Connection .—When the machine to which transfer is made is connected 
directly to the motor without interposition of extra boxes or gearing 
and with shafting directly in line, no extra friction is involved and no 
loss is sustained. (See Figs. 179 and 180.). 

Shafting .—Where a long shaft is directly connected to the source 
of power without gearing, the loss is in proportion to the number of 
bearings, their lubrication, arrangement, and alignment. In shop 
systems the losses, including belt and shaft systems, are often from 1 5 
to 50 per cent with full loads, and are much greater proportionally for 
light loads. 

Gearing. —Bevel-gearing, used to turn a right angle with shafting, 
frequently uses from 15 to 25 per cent of power transmitted, even 
where cut gears are used. 

In gear-trains or worm-gearing, 40 per cent of the power, or more, 
may be consumed, according to the construction and complication. 

Belts .—The loss in simple belts is usually from 5 to 15 per cent; 
tight belts cause excessive friction in bearings and consequently large 
losses. 

Rope Gearing .—With the American system of rope transmission 
the loss is less than with belts, and in single transmission will vary from 
3 to 10 per cent. (See Fig. 62, page 302.) 

Wire-rope Gearing —Unwin gives the efficiency of wire-rope gear¬ 
ing at full load from Zeigler’s experiments as follows: 

Efficiency = .967^ 2 \ 


for T/intermediate and two terminal stations. 








Fig. iSo. 


Electric Pumping-plant, 

Front View. 


DeKalb, Illinois. 


59i 

















Fig. iSo.—Electric Pumping-plant, DeKalb, Illinois. 

Rear View. 


593 














CLASSIFICATION OF PUMPS . 


595 


Pneumatic Transmission. —Friction losses are from 3 to 8 per cent 
per mile. The efficiency of motors varies from 40 per cent, when air 
is used cold, to as high as 70 per cent, when the air is reheated before 
use. 

Hydraulic Transmission. —This method of transmission can be 
calculated from friction tables, and the efficiencies of the class of pumps 
used as given herein. 

Electrical Transmission. —The efficiencies of electrical transmission 
can be calculated from the efficiencies of the electrical machinery, 
together with the line and transformer losses, which in good practice 
is not more than from 5 to 10 per cent. 


THE PUMP IN GENERAL. 

672. Classification of Pumps. —The function of all pumping-ma¬ 
chinery for water-works purposes is to take water from some given 
source and move it to a new position. 

TABLE NO. 90 . 


P 

Oh 


tn 

Oh 


CLASSIFICATION OF PUMPS. 


f f 




"O 

V 

u 

cd 

. TL 

c-c c r. 

s w I 

u 3 ' 

3 o 

Ch > 

M <D 

Q 3 
o 

in 

< 


Recipro¬ 

cating. 


. . ( Double. 

Actlon . \ Single. 


Class. 


I 


Type, 


Piston. 
Plunger. 

Power... 


Inside-packed. 

Outside-packed. 

Center-packed. 

( Single. 

- Duplex. 

( Triplex. 


f 


j High-pressure. 


A 


Steam. -J 


Application... | Co « p P und _ 

( Direct-acting. 

Arrangement. Crank & fly-wheel. 

f ( Compensator. 

TT , ,. ( Direct-acting. 

Hydraulic. } Crank and fl 6 y . wheel . 

Vertical. 

Horizontal. 


Rotary. 
Air-displacement. 
Steam-vacuum. 
Continuous-flow 


Arrangement. | 

j Surface (suction). 

I Use .( Submerged or deep well. 


Impeller. 

Continuous applica¬ 
tion through some - 
mechanical agency 
or medium. 


f Screw. 

J Chain. 

* * } U pump. 

(_ Double-acting. 

f T 11 1 Opene 

Im P eIler . 1 Closer 


I 

Centrifugal... 


Closed. 

_ { Side suction. 

Case.i 


Double suction. 

Horizontal. 

Vertical. 


Arrrangement. 

Water. 

Jet.-j Steam. 

v ( Air. 

Impulse (as name implies). Water-ram. 

v . ( Wheel. 

Bucket (receptacle alternately filled and emptied)., j g an( j > 






















596 


P UMPING-MA CHINE R Y. 


Pumps may be classified in various ways, but for the consideration 
of their mechanical action they may be best considered under the fol¬ 
lowing heads: 

1. Displacement-pumps. 

2. Impeller-pumps. 

3. Impulse-pumps. 

4. Bucket-pumps. 

The various subdivisions of the classification are shown in Table 
No. 90. 

(1) Displacement-pumps . 

673. Displacement-pumps are those in which the volume of water 
raised is forced from the pump-chamber by absolute displacement by 
some mechanical agency. 

674. Reciprocating-pumps.—Of displacement-pumps the ordinary 
reciprocating-pump is the most common and well-known variety. In 
reciprocating-pumps a piston or plunger (which is the displacing 
agency) reciprocates in a closed cylinder provided with the necessary 
inlet- and outlet-valves, and alternately inspires and discharges the 
water from the cylinder. Such pumps are single-acting when one end 
of the plunger only acts on the fluid column (Figs. 181 (a) and 187), and 
are double-acting when the cylinder is so constructed that the pump 
will act on both the forward and the return stroke (Figs. i8i(£), 183, 
184, and 186). Piston-pumps are those in which a finished cylinder is. 
tightly fitted by a reciprocating-piston (Figs. 181 [a] and 183). 

Plunger-pumps are those in which the reciprocating part is a solid 
plunger which does not come in contact with the cylinder-walls. 
These plungers alternately enter and withdraw from the cylinder 
through packing-glands(Figs. i8i(£), 184, 186, and 187). The methods 
of packing plunger-pumps divide them into the additional classes of 
inside (Figs. 184 and 186), outside (Fig. 187), and outside center- 
packed (Fig. i8i(/;)) plunger-pumps. The differential plunger-pump 
(Fig. 181 (r)), while it inspires only on the upward stroke, is, on account 
of the design of the plunger, double-acting on the discharge. 

Fig. 181 (^/) shows a reciprocating piston-pump called a U pump, in 
which the valves are placed in the piston and the flow is in one direc¬ 
tion, with no reversing of the current of water. The most serious 
defect in most reciprocating-pumps is the reversal of the current, which 
is here eliminated. These reversals may cause a considerable loss of 
energy and produce violent and injurious shocks; and on account of 
this defect the number of reversals of most reciprocating-pumps must 


D ISP LA CEMENT-P UMPS. 


59 ? 



(a) Single-acting Piston-pump. 



( 6 ) Outside Center-packed Double-acting 
Plunger-pump. 




(e) Rotary Pump. 

Fig. 181.— 



Types of Pumps. 




































































































59 8 


P UMPING-MA CHINER Y. 



(<r) Air Displacement-pump. (<f) Air Lift-pump. 



xTr 


(*) Vacuum-pump. 

Fig. 182.—Types of Pumps. 

















































































D ISP LA CEMENT-P UMPS. 


599 


be limited. It is therefore possible to run pumps of long stroke at a 
higher piston-speed than those of short stroke. The ordinary recip- 
rocating-pump of io- or 12 inch stroke and limited valve-area should 
seldom be operated at a greater rate of speed than 100 feet per minute, 
while pumps of long stroke and ample valve-area are sometimes 
operated at 300 to 400 feet of piston-travel per minute. 

There is no such limit necessary with pumps of the type shown in 
Fig. 181 (d) y and hence these pumps may be operated at much higher 
speeds. The speed in this case is limited by the necessity of limiting 
the velocity of the water in its passage through the valves. 

In Figs. I 81 (a), (h) } (y), and (d) the water end only of the pump 
is shown. The piston- or plunger-rods may be operated by a connect¬ 
ing-rod and crank to which power is furnished by any form of motor, 
or a second cylinder may be attached to the other end of this rod and 
the water end operated by hydraulic or steam power directly. The 
arrangement of the pump for the application of power gives rise to the 
additional classification of reciprocating-pumps into power (Figs. 179 
and 180), steam (Figs. 183-187), and hydraulic pumps. Power- 
pumps include all that class of pumps which require an independent 
motor for their operation. The term “power-pump,” however, 
includes all other forms of pumps besides the reciprocating variety, 
which are operated by independent motors. Reciprocating power- 
pumps may be Single-cylinder, Duplex, or Triplex, in accordance with 
the number of cylinders of which the pump is composed. 

675. The Steam-pump. —The steam-engine can be applied, in 
common with other motors, to the operation of power-pumps; and 
such an arrangement when properly made is highly efficient and worthy 
of careful investigation and consideration. Such an arrangement 
involves the use of two separate machines. In a large and important 
class of pumping-machinery the steam- and water-cylinders are placed 
in the same machine and in such cases are best considered together. 
Such pumps are called “Steam-pumps.” 

Numerous varieties of this class of pumps are in use. From the 
methods of application of steam this class of pumps is divided into 
“high-pressure” steam-pumps, which include all those in which the 
steam is used at its initial pressure for the full length of the stroke in the 
cylinder and not again used, and “ compound ” steam-pumps, in which 
the steam is used expansively in two or more cylinders. The arrange¬ 
ment and design of the pump give rise to other divisions. In the direct- 
acting pump the steam-piston is connected directly by means of a 
piston-rod with the pump-piston or plunger, the piston-rod being com- 


boo 


P UMPING-MA CHINER Y. 


mon to both steam-piston and water-plunger (Figs. 183 and 184). In 
steam-pumping machinery of this class having only one set of steam- 
cylinders the steam must be used at its initial pressure for the full length 
of the stroke, as in the simple form of this pump (Fig. 183) there are 
no parts with the function to receive, store, and finally give up the energy 
delivered by the steam at the beginning of the stroke as must be 
done when steam is used expansively. Consequently in this form of 
pump the only method of using steam is to exhaust it from the high- 
pressure cylinder directly into the low-pressure cylinder, and use it in 
both cylinders for the full length of the stroke and without the use of cut¬ 



offs. To overcome this disadvantage and to attain the economy possible 
with greater rates of expansion, and still obtain the compactness of this 
type of pumping-machinery, various types of compensators have been 
introduced. The Worthington device (Fig. 184) is perhaps the best- 
known type. In this machine the energy of the steam at the beo-innino- 
of the stroke not only overcomes the resistance of the water pumped, 
but also forces the hydraulic pistons at the front end of the pump against 
a fixed pressure stored in an accumulator. When the center of the stroke 
is reached this stored energy is gradually returned to the pump after the 
steam is cut off and when it is expanding in the cylinder. A decided 






































































































































































D ISP LA CEMENT- P UMPS. 


OOI 



Fig. 184. _Worthington Compound Direct-acting Pump with Compensator. 






































































































































602 


P UMPING-MA CHINEE Y. 



Fig. 185. —Heisler Pump with Compensator, 
















D ISP LA CEMENT - P LIMPS. 


603 



Fig. 186.—Gaskill Crank and Fly-wheel Pumping-engine. 
















































































































































































6 o 4 


PUMPING-MA CHINER Y. 



Fig. 187.—Allis Vertical Tripi. 


e-expansion Pumping-engine. 






























































































































































































D ISP LA CEMEK T-P UMPS. 


635 

increase in the economy of operation of this type of pumps results. 
Another type of compensator of considerable promise is the Heisler 
Compensator (Fig. 185;. In this form of compensator the cylinder of 
one side at full steam-pressure transmits a portion of its force to aid 
the other side, which is working expansively. 

The greatest economy in steam-pumping machinery has been 
developed by what is known as the crank and fly-wheel types of steam- 
pumps. Fig. 186 illustrates the Gaskill horizontal type of crank and 
fly-wheel pumps, and Fig. 187 illustrates the Allis vertical crank and 
fly-wheel type now manufactured by most of the leading pump-makers 
of the United States. 

Hydraulic pumps are pumps arranged very much after the style of 
direct-acting high-pressure steam-pumps, but in which water under 
pressure is used in the power-cylinder. They are not in common use, 
but are occasionally applicable. The exhaust from the power end is 
often wasted into the discharge-pipe from the pump end. 

676. Rotary Pumps. —In the rotary type of displacement-pumps two 
revolving pistons rotate in a pump-case, which they accurately and 



completely fill (Fig. 181 (<?)); the rotation of these pistons alternately 
inspires and discharges the water to be raised. 1 hese pumps act without 
the use of suction- or discharge-valves. A plant consisting of two such 
pumps operated by a turbine water-wheel, as installed at Connersville, 
Indiana, for city water-works purposes, is illustrated in Fig. 188. 










































































6o6 


PUMPING-MA CHINER V. 


677. Air and Steam Displacement-pumps. —Other forms of displace¬ 
ment-pumps are those which use air or steam as the displacing agency. 
A common type of air displacement-pump is the Merrill Pump, which 
consists of two cylinders, set below the water-surface; the water is 
admitted to each cylinder alternately by gravity and is forced from the 
cylinder by the direct pressure of compressed air, which is then ex¬ 
hausted into the atmosphere. In the Harris displacement-pump (Fig. 
182 (c )) the air used to displace the water is returned directly to the inlet 
of the compressor, and is forced by the compressor into the second 
chamber, thus utilizing the work already done and effecting a consider¬ 
able economy in the use of air. The steam vacuum-pump (Fig. 182 (e) ) 
operates on somewhat similar lines; but in this case the condensing of 
the steam is an important factor. Steam is admitted to a chamber and 
condensed therein by a spray of water, thus creating a Vacuum which 
inspires the water; the steam is again applied at full boiler-pressure 
and the water forced by the incoming steam through a discharge-valve 
and pipe, after which the steam is again condensed and the operation 
repeated. Such pumps commonly consist of two chambers, so that a 
comparatively continuous discharge of water results. 

678. Continuous-flow Pumps- An additional variety of displace¬ 

ment-pumps, which differ from those described, are the continuous-flow 
pumps. The most common type of these pumps is the ordinary 
chain-pump, where enlarged piston-links on the chain partially or com¬ 
pletely fill a pipe or passage through which they pass in one direction. 
As the chain passes below the water and into the pipe, the spaces 
between the piston-links are filled successively and the water discharged 
at the outlet as the pistons pass it. The screw-pump also has a similar 
action, the displacement being produced by the screw-blade. The 
“U” type of pump (Fig. 181 (d)) is a less-known variety of the 
same class. A third type of continuous-flow pump is the Johnson 
Deep-well Pump. In this pump, by the use of a Whitworth quick-return 
motion, the double pistons make a quick down-stroke, during which 
time they are free from load, and a slow up-stroke under load. One 
piston of this pump is always on the up-stroke. 

(2) Impeller-pumps. 

679. Action of Impeller-pumps. —The second great class of pumps 
is that of the Impeller-pumps, in which a volume of water is moved 
by the continuous»application of power through some mechanical 
agency or medium. These pumps consist of the centrifugal pumps 
and the various jet-pumps. In the displacement-pump, previously 


/MPE LLER- P UMPS. 


Coy 


described, the motive energy is delivered to the water by a direct 
pressure which displaces the water and which must be equal in amount 
to the head against which the water is pumped and to various fric¬ 
tion losses in the pumping-machinery and discharge-pipes. In the 
class of Impeller-pumps the energy is applied to the water by means 
of pressure due to the velocity of either a mechanical agency, as in the 
centrifugal pumps, or of a fluid agency, as in the jet-pumps. 

680. Centrifugal Pumps.—For falling bodies we have the well¬ 
-¬ 
known formula h — —; that is to say, the velocity v is generated by 

a fall from the height h ; consequently when we reverse the action and 
generate pressure by the application of velocity we should, theoreti¬ 
cally, have the same condition, and a velocity v — V 2 gh should be 
capable of generating a head h. In the centrifugal type of pump (Fig. 
181 (f)) the velocity of the periphery of the impeller must ordinarily 
exceed the velocity given by the above formula. A pump which acts 
strictly as a centrifugal pump must, however, have straight radial 
vanes or impellers. As soon as the vanes are curved, as is done in 
practically all centrifugal pumps now made (Fig. 189), an additional 



Fig. 189. —Section of Rockford Centrifugal Pump. 


force results, and the pump ceases to depend solely on centrifugal 
force. The greater the curve of the vanes the more important becomes 
the action of the new force, which is the resultant of the pressure 
exerted by the inclined surface of the vane, and which acts more with a 
displacement than a centrifugal effect, as in the case of the screw-pump. 








































6o8 PUMPING-MACHINERY. 

Centrifugal pumps may be classed in various ways according to> 
their design and arrangement, as shown in the table of classification. 
Their selection depends on the various uses to which they are to be 
put, the method selected for the application of power, and various 
other factors incidental to the installation. 

Fig. 189 illustrates a vertical side-suction centrifugal pump with 
impeller of the inclosed type, as used in the Rockford, Illinois, deep- 
well pumping-plant (see Fig. 62, page 302)'. 

681. Jet-pumps. —Jet-pumps (Fig. 182 (#)) are arranged to utilize the 
velocity energy of water-, steam-, or air-jets. In all of this class of 
pumps a moving jet of the liquid used is delivered through a restricted 
throat, drawing with it the water to be raised, to which the velocity 
energy is delivered. Water, steam, and air have each particular 
attributes of their own in their application to this class of pumps. The 
air especially has an additional effect not due to the velocity, in that it 
reduces the specific gravity of the rising column of water, and may, 
under proper conditions, cause an overflow in the column so lightened 
(Fig. 182 (d) ). 

This class of air-pumps, called “ air-lift ” pumps, has recently been 
quite widely applied to raising large quantities of water from bore-holes. 
These pumps are not highly efficient, but are capable of raising a larger 
amount of water from a small hole than any other method. For 
reasonable efficiency the submergency of the discharge-pipe should be 
at least 60 per cent of its total height, or one and one-half times the 
height to which the water is raised above the surface. 

The formula commonly used for determining the relation of the 
various factors in an air-lift problem is 

125-4 

q = ~lT’ 

in which q = gallons of water per minute; 

A — cubic feet of free air per minute; 

h — height of lift in feet from water-surface to point of dis¬ 
charge. 


(3) Impulse-pumps. 

682. The third class of pumps comprises those of the impulse type, 
which raise water by the periodical application of force.suddenly applied 
and suddenly discontinued. The hydraulic ram is the principal repre¬ 
sentative of this class (Fig. 182 (&)). In this pump the pulse-valve or 



PUMP DETAILS . 


609 

waste-valve, is opened automatically either by gravity or some other 
agency (such as a spring, as in the figure) properly applied. The water 
in the drive-pipe wastes through this valve, acquiring a velocity which 
in turn generates sufficient friction to suddenly close the valve, thus 
causing an impact or impulse which, when properly applied, opens the 
check-valve and delivers a certain proportion of water into the air- 
chamber and delivery-pipe. As the impulse dies away the waste valve 
again opens and the cycle is repeated. 

(4) Bucket-pumps. 

683. The fourth class of pumps is composed of the bucket-pumps, 
which include all those in which definite receptacles are alternately- 
filled, raised, and emptied. These pumps are often of the form of the 
continuous-conveyor type, in which a series of buckets attached to a. 
belt and chain are dipped in the water, filled, elevated, and emptied. 

PUMP DETAILS. 

684. General Rules. —The class of any pump must modify largely 
the details used in its construction. A few general rules will apply, 
however, in all cases. 

All pumps should be so designed and connected as to admit the 
free and unrestricted flow of water. They should be free from all air- 
traps, and when changes in the direction of flow are necessary, large 
easy bends should be used. 

685. Valves. —Almost all displacement-pumps require the use of 
admission- and discharge-valves. These valves are a serious source of 
loss of efficiency in this class of machinery. Frequently as high as 12 
to 15 feet of head is lost in the valve- and water-passages even of high- 
grade pumping-engines. 

The primary requisites of pump-valves are as follows: 

They should close tightly, to avoid loss from leakage. 

They should close promptly, to avoid loss from slip. 

They should have small lift, to permit of prompt closing. 

They should have large waterways. 

They should open easily and without large extra pressure. 

They should present small resistance to flow, in order to reduce 
the friction losses to a minimum. 

They should be simple, readily accessible, and readily removable 
to facilitate repairs. 

The type of valve most widely used is shown in Fig. 190 (a). These 


6iO 


P UMPING-MA CHINER Y. 



(a) Ordinary Valve. (6) Method of Grouping Valves. 



(c) Troy Valve. 



(*) Walker Valve. 



( d) Battle Creek Valve. 



(/) Riedler Valve. 




(£•) Ball Valve. 
Fig. 190.- 


(h) Cone Valve. 
-Types of Pump-valves. 


















































PUMP DETAILS. 


6l I 

valves are ordinarily from 3^ to 4J inches in diameter. The valve- 
seat, stem, cover-plate, and spring should be of bronze. 

True cylindrical springs are preferable to conical springs. The 
disks should be of medium hard India rubber, vulcanized sufficiently 
to give it firmness. For hot-water pumps this disk should be of hard 
rubber. The lift of the valve is limited by the stem-head, and the stem 
prevents its drifting sidewise. A sufficient number of these valves are 
grouped in the valve-chamber to give the desired waterway. I11 poor 
pumps this is commonly not over 25 per cent of the plunger area; 
while high-grade pumps will have a free waterway of from 50 to 100 per 
cent of the plunger area, according to the speed of operation and 
number of reversals of the plunger. 

Fig. 190 ($) shows the arrangement of these valves as commonly 
used in large pumping-engines. Several of these groups may be used 
in a single valve-chamber. 

Fig. 190 (c) shows the Troy valve used in the Gaskill pumping- 
engine. It is a small valve having a diameter of about if inches 
No spring is used with this valve. 

Fig. 190 ( d ) shows a metal valve used in the Battle Creek pumps. 
In this valve the lift is limited by the walls of the valve-chamber. 
The curved center guides the liquid through the opening with minimum 
friction and small eddy losses, as the liquid leaves the curve on a tan¬ 
gent when the valve is fully open. 

Fig. 190 (e) shows the form of valves used in the Walker pump. 
The valve disk or cover is of rubber of a rectangular shape thickened 
at the sides, the center forming a hinge and the sides forming the 
valve-covers. The upper portion of the figure shows the arrangement 
of the suction-valves; the lower portion shows the discharge-valves. 

Fig. 190 (/) shows the Riedler valve. Only one valve of this type 
is used on each inlet or outlet of the Riedler pumps. This valve is 
mechanically closed just as the direction of motion of the pump-piston 
is reversed. By the use of this valve, large waterway is provided, and 
by its mechanical closing, slip and pound is prevented when the pump 
reverses. 

Fig. 190 (g) shows a ball valve which is commonly used in deep- 
well pump-cylinders. The valve is usually a bronze sphere and seats 
in a bronze ring simply by its own weight.. Its lift is limited as shown 
in the cut. Groups of such valves are sometimes arranged in valve- 
chambers for reciprocating-pumps. 

Fig. 190 (h) shows the Downie cone valve, which is also used for 
deep-well cylinders. This valve consists of two cones, the outside one 


612 


PUMPING-MA CHINER Y. 


being movable. When this outside cone is seated the valve is closed, 
the solid metal of each cone closing the apertures in the other. When 
the valve is raised the apertures in the cones are opposite and the 
water passes readily through the openings. 

Rotary and centrifugal pumps can be operated without valves of 
any description, but it is desirable with these pumps, as with all 
others which are used for water-works purposes, to use a check-valve 
on the discharge, so that in case any accident should happen to the 
machinery, the reservoir, stand-pipe, or other device for storing water 
will not be emptied through the broken pump into the pumping-station. 
In the case of rotary and centrifugal pumps the check-valve is particu¬ 
larly necessary, as when the power ceases to be applied the pump will 
discharge the stored water back through the pump and suction-pipe 
into the source of supply. 

686. Air and Vacuum Chambers. —All displacement-pumps except 
the continuous-flow variety, and even those unless the continuity of 
flow is perfect, should be provided with vacuum- and air-chambers on 
the inlet- and discharge-pipes in order to take up the irregularities of 
flow due to intermittent or irregular action and prevent injurious and 
sometimes destructive shocks. 

The size of air-chamber depends on the condition of working. 
Since the function of the air-chamber is to eliminate irregularities, the 
greater the irregularities the larger the chamber should be. Hence, 
with a high-speed pump or a pump forcing water through great length 
of pipe or against a high head, the air-chamber should be enlarged over 
what would be needed with slow-running pumps and low lifts. 

Triplex pumps under low lifts may be provided with air-chambers 
of a capacity equal to a single displacement of the piston, while for 
single-cylinder, double-acting pumps the air-chamber should be from 
six to eight times this size. Means for supplying air-chambers with air 
should also be provided. In suction-pumps this can be readily accom¬ 
plished by connecting a small check-valve with a pump-chamber so 
that when the pump inspires it will draw in a small amount of air with 
the water. A globe valve outside of the check-valve will control the 
operation of the air-inlet as may be desired. 

It is desirable to provide air-chambers with a gauge-glass, so that 
the amount of air in the chamber will be known (Fig. 179). 

687. Inlet- or Suction-pipes. —Pumping-machinery may receive the 
water to be pumped in two ways. 

First , the water may flow to the machine by gravity, the machine 

k - 


P UMP DE TAILS. 61 3 

being below the water a depth at least equal to the sum of the velocity 
and friction heads. 

Second , the water may be raised through a pipe into the machine 
by atmospheric pressure or suction. 

Suction consists in creating a more or less perfect vacuum in the 
suction-chambers and suction-pipe and filling the same with water by 
atmospheric pressure. Before a suction-pump will work properly it 
must be able to create such a vacuum or to “prime” itself. The 
priming of a pump in which there is no water requires either the filling 
of the pump with water from some other source and the consequent 
expulsion of the air, or that the empty pump shall act as an air- 
pump and thus remove the air. A centrifugal pump cannot act as an 
air-pump. It must therefore be below the water to prime itself. In 
order to prime a pump which cannot act as an air-pump it must be pro¬ 
vided with a foot-valve which will prevent the loss of water from some 
higher source, or a priming-pump (i.e., a small air-pump) must be 
attached to it. 

Reciprocating-pumps can be primed by the piston action much 
more readily than rotary pumps, but, especially on high lifts, should 
be provided with priming-pipes. 

For perfect suction and satisfactory operation care must be taken 
to secure the following conditions: 

1. The openings between the moving and fixed parts of the pump 
must be as small as possible, that is, the pump must be well packed 
between the fixed and moving parts. 

2. The suction-chambers and pipes must be air-tight. 

3. All air-traps must be avoided in all suction members. 

4. All unnecessary bends must be avoided, and the suction-pipe 
should be made as short and direct as possible. The pump should be 
placed as near the water as possible, and the suction-pipe should be of 
proper size. The possibility of suction is limited (see Table No. 37, 
page 214). 

The amount of available suction-head must never be less than the 
sum of the following heads commonly lost in suction-pipes and the 
suction-passages of pumps: 

1. Influx loss at end of suction-pipe (see eq. (36), page 238). 

2. Velocity loss in suction-pipe (see Art. 657). 

3. Friction loss in suction-pipe (see Fig. 34, page 233). 

4. Friction loss in suction-valve and water-passage of pump (see 

Art. 685). 


6 14 


P UMPING- MA CHINER Y. 


5. Acceleration head, or the pressure necessary to accelerate the 
<vater where the flow is not uniform. 

6. Vapor tension of water (see Table No. 38, page 215). 

If the sum of these losses together with the head against which the 
water is to be raised by suction is greater than the available atmos¬ 
pheric pressure, the pump will not work to its proper capacity and may 
not raise the water at all. 

688 . Location of Pumping-machinery with Respect to the Level of the 
Water Drawn from. —The conditions under which the water-supply 
must be obtained will to a large extent control the type of machinery 
which must be used. As before noted, it is always desirable to place 
the water end of the machinery as near the water as possible, while the 
power end must usually be placed above high water, or, if placed 
below the water, it must usually be arranged in a water-tight shaft or 
compartment. The ordinary horizontal type of reciprocating pump¬ 
ing-machinery should seldom be placed more than 18 feet above the 
lowest water it will be called upon to handle. A suction lift of 24 
to 26 feet is, however, sometimes possible. Where the distance 
from pump to water-surface is greater than the maximum, and 
especially where large volumes of water are to be handled, such lifts 
become hazardous or impossible and other types of pumping-machinery 
must be used or other methods of locating the machinery employed. 

The most obvious method of reaching water when it is below suction 
distance is to sink the pump to such a depth below the surface as to 
bring it within easy suction distance of the water. When the distance 
is not too great and where conditions are favorable, this can readily be 
done, and this method has frequently been employed. 

The water ends of pumps demand but comparatively little attention. 
The flow of water lubricates most of the parts to a considerable extent, 
and such parts as are not in this way sufficiently lubricated can be 
easily cared for by attention at occasional intervals. 

1 he motor end of the pump, however, is usually much more com¬ 
plicated and necessarily requires more particular and constant attention. 
When, therefore, the depth at which the water is obtained is consider¬ 
able, it is often desirable to rearrange the design of the pumping- 
machinery, placing the water end within easy suction reach of the 
supply, and the motor end within ready access from the surface and 
near the boilers or other source of power. This has given rise to 
various types of vertical machinery which fulfill these conditions with 
more or less success. 

The cost involved in the construction of large shafts, especially in 


PUMP UP TAILS. 


615 


unfavorable locations, may make it desirable to economize in shaft 
room. Special types of pumps have been designed to suit these 
requirements, and the same result may be obtained under favorable 
conditions by the enlargement of the base of the shaft and the use of 
ordinary types of horizontal pumps located near the shaft base where 
such arrangement is permissible. The arrangement of the machinery 
with this end in view is shown in the plant installed at Rockford, 
Illinois (page 302). The water end of this pumping-plant consists of 
high-grade centrifugal pumps, while vertical compound condensing 
engines furnish the motive power, and rope transmission is the means 
of connecting pumps and engines. The above arrangement assumes 
the ability to concentrate the water at one central shaft in which the 
machinery is located. This may be done in general in the following 
ways: 

1. By the construction of a large open well in an open or coarse 
water-bearing stratum. Such plants have been satisfactorily adopted 
for small and medium quantities of water. 

2. The various wells may be connected by pipes laid as deeply as 
possible in trenches open from the surface. 

3. The various wells may be connected by tunnels into which the 
water may empty direct, or the wells may be connected by pipes laid 
in the tunnels and connected to the suction side of the pumps. 

Where shaft and tunnel work is expensive it will sometimes become 
desirable to install small isolated plants on each well, which may be 
operated singly or together as the water required demands. For this 
use one or more small shafts may be built and connected directly with 
the water-bearing stratum, or one or more bore-hole wells may be sunk, 
and in such shafts or wells the secondary machinery may be placed. 

Separate steam-pumps may be applied to such wells, but usually 
such pumps are far from economical. Power may, however, be gen¬ 
erated in various ways from a central and more economical generator 
and transmitted to the separate wells by electrical transmission, by 
pneumatic transmission, or by hydraulic transmission. 

At De Kalb, Illinois, where the water is raised from deep wells 
from a depth of 1 50 feet below the surface, electrical transmission is 
used, the water being raised by separate pumps and forced into the 
reservoir near the surface, from which it is taken by the service pumps 
(see Fig. 180). and pumped into the mains and stand-pipe. 

At Peoria, Illinois, Mr. D. IT Maury, Mem. Am. Soc. C. E., has 
developed a unique and efficient method of hydraulic transmission. 
The water which operates the secondary plants is taken from the mains 


616 


PUMPING-MA CHINER Y. 


supplied by the high-duty pumping-engine. The secondary installa¬ 
tions are operated by impulse water-wheels attached to horizontal 
centrifugal pumps. The water used to operate the impulse-wheels 
together with the water pumped by the centrifugal pumps is returned 
to the main-supply well. 

The centrifugal pump is widely used on the Pacific coast for such 
purposes, and for lifts of 150 feet or less can often be operated to an 
advantage. Its use throughout the eastern part of the United States 
is not so general; the plant at Rockford, Illinois, (see Figs. 62 and 
189,) being perhaps the highest lift of any attempted in the East, 
namely, 106 feet, when pumping to the full capacity of the plant. 

DUTY AND EFFICIENCY OF PUMPING-MACHINERY. 

689. Measures of Duty. —While the efficiency of pumping-machinery 
may be measured by the units included in the tables previously given, 
there is also another measure of efficiency which is largely used in con¬ 
sidering pumping-plants and pumping-machinery. This measure of 
efficiency is termed “duty ” and represents the ratio of work done to 
the energy expended in doing it. Duty may be expressed in almost 
any units, but in pumping it usually represents the ratio of foot-pounds 
of work done to a fixed weight of coal, or steam, or to a fixed number 
of heat-units used. 

The terms most generally used to express duty of pumping-engines 
are foot-pounds duty per 100 pounds of coal, per 1000 pounds of steam, 
or per 1,000,000 heat-units. 

It must be understood that the duties expressed in the above units 
are not necessarily equivalent, but vary largely in actual value. For 
example, the Indianapolis Water Company’s engine, built by the Snow 
Steam-pump Company, is said to have developed a duty of 167.8 
million foot-pounds for each 1000 pounds of dry steam, but only 150.1 
million foot-pounds for each 1,000,000 heat-units. 

Duty based on coal is very indefinite, for coal varies largely in its 
potential energy or calorific value (see Table No. 85). 

When coal is considered the plant efficiency must also be included. 
This may include boilers, steam-pipe, feed-pump, heater, etc., which 
have not necessarily any relation to the individual efficiency of the 
pump itself. Duty based on coal should therefore only be used where 
the entire plant is considered and when the class of coal is also 
specified. 

Duty based on steam is more specific, but hardly sufficiently so. 


DUTY OF PUMPING-MACHINERY . 617 


TABLE NO. 91. 

DUTY, CORRESPONDING AMOUNT OF COAL PER H.P. PER HOUR, AND CORRESPONDING 
AMOUNT OF COAL REQUIRED TO RAISE 1,000,000 GALLONS IOO FT. HIGH. 


Duty 
in Mil¬ 
lion 

Ft.-lbs. 

Pounds of Coal 
per H.-P per 
Hour. 

Lbs. per Million 
Gals. 100 Feet 
High. 

Duty 
in Mil¬ 
lion 
Ft.-lbs. 

Pounds of Coal 
per H.P. per 
Hour. 

Lbs. per Million 
Gals. 100 Feet 
High. 

Duty 
in Mil¬ 
lion 

Ft.-lbs. 

Pounds of Coal 

per H.P. per 

Hour. 

Lbs. per Million 

Gals. 100 Feet 

High. 

Duty 
in Mil¬ 
lion 
Ft.-lbs. 

Pounds of Coal 

per H.P. per 

Hour. 

Lbs. per Million 

Gals. 100 Feet 

High. 

I 

I98.OO 

83398 

43 

4.60 

1939 

84 

2.36 

992 

T 25 

I.58 

667 

2 

99.OO 

41699 

44 

4-50 

1895 

851 

2-33 

981 

126 

1-57 

662 

3 

66.00 

27799 

45 

4-40 

1853 

86 

2.30 

969 

127 

1.56 

656 

4 

49-50 

20849 

46 

4-30 

1813 

87 

2.28 

958 

128 

i -55 

651 

5 

39.60 

16679 

47 

4.21 

1774 

88 

2.25 

947 

129 

i -53 

646 

6 

3300 

13899 

48 

4. 12 

1737 

89 

2.22 

937 

130 

1.52 

641 

7 

28.29 

H 9 I 4 

49 

4.04 

1702 

90 

2.20 

926 

131 

1. 5 i 

636 

8 

24-75 

IO424 

50 

3-96 

1668 

9 i 

2. l8 

916 

132 

1.50 

632 

9 

22.00 

9266 

5 i 

3-88 

1635 

9 2 

2.15 

906 

133 

1.49 

627 

IO 

19.80 

8340 

52 

3.80 

1604 

93 

2.13 

890 

*34 

1.48 

622 

ii 

18.00 

7561 

53 

3-73 

1573 

94 

2 . II 

887 

135 

1.47 

6l8 

12 

16.50 

6930 

54 

3.66 

1544 

95 

2.08 

878 

136 

1.46 

613 

13 

15-23 

6413 

55 

3.60 

1516 

96 

2.06 

868 

137 

i -45 

609 

14 

14.14 

5937 

56 

3-53 

1489 

97 

2.04 

859 

138 

1-43 

604 

15 

13.20 

556 o 

57 

3-47 

1463 

98 

2.02 

851 

139 

1.42 

600 

16 

12.37 

5212 

58 

3-41 

1437 

99 

2.00 

842 

140 

1.41 

595 

17 

11.64 

4906 

59 

3-35 

1414 

100 

1.98 

834 

141 

1.40 

591 

18 

11.00 

4633 

60 

3-30 

1389 

IOI 

I.96 

825 

142 

1-39 

587 

19 

10.42 

4384 

61 

3-24 

1367 

102 

I.94 

817 

M 3 

1.38 

583 

20 

9.90 

4170 

62 

3-19 

1345 

103 

I.92 

809 

144 

i -37 

579 

21 

9-43 

3971 

63 

3 -i 4 

1323 

104 

1.90 

802 

*45 

1.37 

575 

22 

9.00 

3791 

64 

3-09 

1303 

105 

I.89 

794 

146 

1.36 

57 * 

23 

8.60 

3626 

65 

3-04 

1283 

106 

I.87 

786 

147 

i -35 

567 

24 

8.25 

3475 

66 

3.00 

1263 

107 

I.85 

779 

148 

1-34 

563 

25 

7.92 

3336 

67 

2-95 

1244 

108 

I.83 

772 

149 

i -33 

560 

26 

7.61 

3208 

68 

2.91 

1226 

109 

1.82 

765 

150 

1.32 

556 

27 

7-33 

3089 

69 

2.87 

1208 

no 

I • 80 

758 

151 

1. 3 i 

542 

28 

7.07 

2978 

70 

2.83 

1191 

III 

I.78 

75 i 

152 

1.30 

539 

29 

6.83 

2876 

7 i 

2-79 

1174 

112 

i -77 

744 

153 

1.29 

534 

30 

6.60 

2780 

72 

2.75 

1158 

113 

i -75 

738 

154 

1.28 

53 i 

31 

6.38 

2690 

73 

2.71 

1142 

114 

1.74 

73 i 

155 

1.27 

528 

3 2 

6.18 

2606 

74 

2.67 

1127 

115 

1.72 

725 

156 

1.27 

525 

33 

6.00 

2527 

75 

2.64 

1112 

Il6 

1 • 7 1 

719 

157 

1.26 

522 

34 

5.82 

2433 

76 

2.60 

IO97 

117 

1.69 

713 

158 

1.25 

518 

35 

5-65 

2383 

77 

2-57 

1083 

Il8 

1.68 

707 

159 

1.24 

5*6 

36 

5-50 

2316 

78 

2-54 

IO69 

119 

1.66 

701 

160 

1.24 

5 ii 

37 

5-35 

2254 

79 

2.50 

1055 

120 

1.65 

695 

161 

1.23 

508 

38 

5-21 

2194! 

80 

2.47 

IO42 

121 

1-64 

689 

162 

1.22 

504 

39 

5-07 

2138 

81 

2.44 

1029 

122 

1.62 

683 

163 

I -21 

502 

40 

4-95 

2085 

82 

2.41 

1017 

123 

1.61 

678 

164 

1.21 

499 

4 1 

42 

4-83 

4.71 

2034 

1985 

83 

2.38 

1004 

124 

1.60 

672 

165 

1.20 

496 





















































6i8 


P UMPING’MA CHINER Y. 


Both theory and practice show that, with suitable conditions, steam at 
150 pounds pressure has a greater value than steam at 90 pounds 
pressure. The entrained water from the boiler and the condensation 
in the steam-pipe also modify the results. When duty is based on the 
weight of steam used, the terms dry steam and a specified pressure 
should also be included. 

In Table No. 91 the relation of duty to coal-consumption and 
steam-consumption per horse-power per hour is shown. 

A table of the relations of duty to steam-consumption per horse¬ 
power per hour, and of steam required to raise 1,000,000 gallons ioo* 
feet high, may be obtained by multiplying the figures for coal in the 
respective columns by 10. A similar table for heat may be obtained by 
multiplying by 10,000. The corresponding duty values in such tables 
are not, however, necessarily equivalent. 

The duty of any pumping-engine or pumping-plant may be calcu¬ 
lated from the formula: 


Duty i= 


weight of water pumped X head X duty unit 
amount of energy used 


The “duty unit” is 100 for coal, 1000 for steam, and 1,000,000* 
for heat-units. The “amount of energy used ” is the total weight of 
coal or steam, or the number of heat-units used. 

It may be noted from Table No. 82 that with perfect efficiency the 


following duties should be developed: 

„ Foot-pounds. 

100 pounds average anthracite coal. 1,140,548,000 

100 pounds average bituminous coal. 991,172,000 

1000 pounds steam (approximate). 778,000,000 

1,000,000 pounds British thermal units. 778,000,000 


From the above it will be noted that 100 pounds of average coal has 
a greater theoretical value than 1000 pounds of steam. Under good 
average conditions, however, not more than 10,000 British thermal- 
units per pound of coal can be transformed into the actual potential 
energy of steam, and in ordinary practice the amount transformed is 
usually much less. 

The above theoretical equivalents should be compared with the 
results usually obtained in practice as shown in Table No. 92. 

690. Ordinary Duty and Efficiency of Pumping-machinery. _Table 

No. 92 shows, first, the ordinary duty and efficiency of steam pump¬ 
ing-machinery; second, the duty and efficiency of pumping-plants 








DUTY OF PUMPING-MACHINERY. 



TABLE NO. 92 . 

DUTY OF PUMPING-PLANTS. 


Class. 


High-duty engines. 

Pumping-engines. 

Large well-designed steam-pumps... 
Ordinary well-designed steam-pumps 

Direct-acting deep-well pumps. 

Vacuum-pumps. 

Jet-pumps. 


I 

I 

I 

I 

I 

I 


Duty per iooo 
Pounds Steam. 

Pounds Steam 
per A.H.P. 
per Hour. 

Theoretical 
Efficiency. 
Per cent. 

Max. 

160 

12.3 

20.6 

Min. 

100 

19.8 

12.9 

Max. 

100 

IQ.8 

12.9 

Min. 

75 

26.4 

9.8 

Max. 

40 

49-5 

5.2 

Min. 

20 

99 .O 

2.6 

Max. 

20 

99 .O 

2 . 6 

Min. 

10 

I 98 .O 

1.3 

Max. 

6 

330.0 

.77 

Min. 

2 

990 .O 

. 26 

Max. 

8 

247.5 

1.04 

Min. 

2 

99 O.O 

. 26 

Max. 

4 

495-0 

• 52 

Min. 

1 

1980.0 

.13 


Average Duty of Power-pumps with Direct-connected Engine . 

Pump Efficiency 75 ter cent. 


Simple high-speed engine, non-condensing. 

Simple Corliss non-condensing. 

Simple Corliss condensing. 

Compound high-speed condensing. 

Compound Corliss condensing. 

Triple-expansion condensing. 


Max. 

47 

42.0 

6.1 

Min. 

37 

53-5 

4 • 8 

Max. 

58 

34 -o 

7-5 

Min. 

47 

42.0 

6.1 

Max. 

75 

26.4 

9.8 

Min. 

67 

29. 5 

8.6 

Max. 

75 

26.4 

9.8 

Min. 

58 

34 -o 

7 • 5 

Max. 

92 

21.5 

10. 2 

Min. 

75 

26.4 

9.8 

Max. 

114 

17.4 

14.7 

Min. 

99 

20.0 

12.7 


Average Duty of Air-lift Pump with Various Types of Air-compressors. 

Pump Efficiency 25 per cent. 


Compound Corliss condensing. 

Simple Corliss condensing. 

Simple Corliss non-condensing. 

Well-designed high-pressure compressor .. 

Small straight-line. 

*__ ___—- 


Max. 

3 i 

63.8 

4.0 

Min. 

25 

79.0 

3-2 

Max. 

22.5 

88.0 

2.9 

Min. 

18 

110.0 

2.3 

Max. 

14 

141.0 

1.8 

Min. 

12 

165.0 

i -5 

Max. 

12 

165.0 

i -5 

Min. 

8 

247.0 

1.03 

Max. 

10 

198.0 

1.29 

Min. 

6 

330-0 

•77 


composed of power-pumps of 75 per cent efficiency direct-connected to 
various types of steam-engines, with steam-consumption as given in 
Table No. 89; and third, the duty and efficiency of pumping-plants 
composed of various types of air-compressors and the air-lift pump of 

25 per cent efficiency. 









































620 


P UMPING-MA CHINER Y. 


These results may be considered as fair average results of well- 
designed plants. Results much higher may be obtained under ideal 
conditions, and much poorer results are only too common in actual 
practice. 

The efficiency of various power-pumps, and of some other pumps 
before mentioned, is about as follows: 

ORDINARY EFFICIENCY OF PUMPS. 

Minimum. Maximum. 


Reciprocating-pumps. '..... 60 85 

Centrifugal pumps. 50 80 

Rotary pumps.. 5 ° 8° 

Displacement air-pump exhausting into at- ) 

mosphere.) 20 2 ^ 

Harris displacement air-pump. 60 70 

Air-lift pump. 15 40 


With other values from between the limits named above substituted 
in Table No. 92 there will, of course, be corresponding changes in the 
ultimate duty and efficiency of the respective plants. 

691. Methods of Analyzing Losses of Energy. —From statements 
already made it will be seen that a great variation in duty and in 
efficiency exists between thes various types of pumping-plants, and 
consequently in the cost of their operation. Careful analysis of various 
combinations which can be utilized for any place should be made in 
order to obtain a basis for intelligent comparison. This analysis can 
be made either analytically or graphically, but the graphical methods 
possess the advantage of showing at once to the eye the points at which 
all losses occur, and where attempts to economy can best be made. 

A graphical analysis of the power losses in the centrifugal pump¬ 
ing-plant at Rockford, Ill., is illustrated in Fig. 191. The diagram 
to the left illustrates the losses from the fuel used to the indicated 
horse-power developed in the engine. 

The line in this diagram numbered 1 represents, by its length, the 
total energy of the fuel used. It is subdivided into one hundred pajts. 
Diagonal lines drawn from any point on this line to the focal point at 
the right will subdivide every vertical line in the diagram proportional 
to the percentage line of the total energy of the fuel. 

It is found that, on account of natural limitations, not more than 83 
per cent of the actual fuel-value is theoretically available in the furnace. 
The length of the line No. 2 therefore represents the proportion of the 








Total Cr/cAzsy or ftoctL fOQZl /no> gated ftft CftCK.<sY <4m./co 


METHODS OF ANALYZING LOSSES OF ENERGY . 


621 


total energy of the fuel which theoretically should be utilized by the 
boiler. 


In the plant in question only about 75 per cent of the energy 



2 

w 

> 

►— 


p 

I 

w 

p 

o 

<& 

p 


P 

53 

P 

p 


s 

c 

PS 

o 


p- 

u 

2 

w 


p 

< 

o 

p 

p 

P 

r 1 

2 

« 

u 


o 

►-< 

p 

p 

w 



theoretically available is utilized, hence the energy utilized in the 
boiler is represented by line No. 3, which is 75 per cent of the line 
No. 2, or about 62^ per .cent of the total energy of the fuel burned. 


Fig. 191.—Efficiency Diagrams, I^ockfoep Pumping-plant 





















622 


PUMPING-MA CHINEE Y. 


The loss in the steam-pipe is assumed at 5 per cent of the boiler 
energy, hence there is delivered to the engine about 59 per cent of 
the total energy of the fuel. Of the total energy delivered to the 
engine as steam only about 25 per cent is theoretically available in the 
engine. This proportion is represented by line No. 5 of the diagram. 
In the plant in question, the amount actually utilized in the indicated 
horse-power of the engine is about 8^ per cent of the energy delivered 
to it. This amount is represented by line No. 6 of the diagram. 
From this diagram it is also seen that the amount of energy utilized in 
the indicated horse-power of the engine is about 34 per cent of the 
energy theoretically available in the engine and about 5 per cent of the 
total energy of the fuel consumed. 

The percentage line in the right-hand diagram is an enlargement 
of the line representing the energy utilized in the indicated horse-power 
of the engines as shown by line No. 6 of the left-hand diagram. From 
this diagram it will be noted that there is a loss of about 10 per cent 
in engine friction, that is, the actual horse-power delivered by the 
engine is 90 per cent of the indicated horse-power of the engine. 
About 5 per cent is lost in the transmission rope, an additional 5 per 
cent in the pump friction, and about 8 per cent in the friction of the 
water in passing through the pump, the energy actually delivered by 
the pump being about 74.8 per cent of the indicated horse-power of the 
engine. 

From this diagram it will be noted that the actual efficiency of the 
centrifugal pump is about 88 per cent of the power delivered to the 
pumps by the rope-drive. This is an exceedingly high record for a 
centrifugal pump, and it is believed to be the highest results recorded 
for this type of machinery. 

It will be noted from the left-hand diagram that 5 per cent of the 
calorific value of the fuel is utilized in the indicated horse-power of the 
•engine, while by the right-hand diagram about 75 per cent of the indi¬ 
cated horse-power is utilized in the actual water raised. Thus in this 
plant only about 3! per cent of the calorific value of the fuel is realized 
in water pumped. To those who have not before analyzed the losses 
in power transmission, the amount utilized in this plant may seem 
absurdly small. It is, however, exceptionally large for the type of 
plant used. In pumping-engines of medium capacity it is seldom that 
more than 7 or 8 per cent of the fuel is utilized, and in the poorer type 
^of plants the utilization of less than 1 per cent is more often the result. 

A graphical analysis of the probable power losses in the De Kalb, 
Ill., Electric Pumping-plant (see Fig. 180) under domestic service, and 


SELECTION AND ARRANGEMENT OF PUMPING-PLANTS. 623 

from the I.H.P. of the engine, is shown in Fig. 192. In this plant the 
power is generated by the De Kalb Electrical Company at their central 
station and transmitted as a 220-volt direct current for a distance of 
about two-thirds of a mile to the city pumping-station, where the power 



Fig. 192. —Probable Efficiency Diagram of the De Kalb, III., Electric 

Pumping-plant, Domestic Service. 

is used for pumping in the motors and pumps shown in Fig. 180. 
From the graphical diagram it will be noted that the work delivered by 
the pump is about 27 per cent of the I.H.P. If the I.H.P. is but 5 per 
cent of the fuel-value, the total plant efficiency will be 1.35 per cent. 

692. Considerations Influencing the Selection and Arrangement of 
Pumping-plants. —The preceding diagrams, showing the losses in energy 












024 


P UMPING-MA CHI NEK Y. 


due to the transformation of energy from coal burned to water pumped r 
emphasize the fact that energy cannot be transformed or transmitted 
without loss, and, other things being equal, the more directly energy 
is utilized, the more economical the results obtained. Other factors, 
however, must be considered in this connection. A steam vacuum- 
pump is a more direct application of steam than a pumping-engine. 
Steam is, however, here applied in a very extravagant manner, and the 
vacuum-pump can only be used for emergency or occasional purposes 
where simplicity is of more importance than economy. 

A direct-acting high-pressure steam-pump is a more direct applica¬ 
tion of steam than the combination of a steam-engine and power-pump. 
Steam, however, is applied in this steam-pump without taking advan¬ 
tage of expansion, and the expansive use of steam in the steam-engine 
will usually more than offset the greater complication in the application 
of power. 

Other conditions also have an important influence. When small 
amounts of water are to be pumped the cost of attendance may more 
than offset the large energy losses. Thus at De Kalb, Ill., (Fig. 180,) 
it was found that the De Kalb Electrical Company, having an electrical 
plant in constant operation, could furnish electric power at less cost, 
in spite of the large transformation and transmission losses (Fig. 192), 
than the cost at which the city could generate the power for their own 
plant. 

The engineer should, however, aim at simplicity in arrangement 
and avoid all unnecessary complications. All losses should be traced 
and reduced to the lowest practicable amount. 

The plant when selected should be arranged to facilitate its care 
and operation, and due regard should be taken to foresee and provide 
for future repairs and renewals with the least possible expense. 

Fig. 193 shows the arrangement of a small pumping-plant. The 
plant is arranged for future duplication. The boiler is of the internally 
fired Scotch marine type. No brick is used for setting, but the boiler 
is covered with magnesia sectional covering to prevent condensation. 
The coal is brought from the coal-room on a car, being first weighed 
so that a systematic account of fuel used may be kept. The boiler is 
fed either by a direct-acting duplex steam-pump or by an injector. 
The feed-water is pumped from the main suction-pipe through a closed 
heater through which the exhaust steam from the engine is passed. 
All feed-water passes through a meter so that a daily record of evap¬ 
oration may be kept. A high-speed engine furnishes power for 
pumping by direct connection to a triplex power-pump. The steam- 


SELECTION AND ARRANGEMENT OF PUMPING-PLANTS. 625 




F IG . 193 .— Plan and Elevation of Pumping-station, showing Boiler, Power- 

pump, and Direct-connected Engine. 




















































































































































■626 


P UMPING-MA CHINER Y. 


pipe is as direct as practicable—enough angles being used to allow for 
expansion. To prevent radiation and condensation the pipe is covered 
in a manner similar to the boiler. 

The engine- and boiler-rooms should be large enough to allow 
plenty of room to work around the machinery. They should be well 
lighted and reasonably well finished. A good building and plenty of 
light are great inducements to the proper care of machinery. 

693. Capacity of Pumping-machinery. —Two methods of pumping 
are possible for water-works purposes. One is that of pumping into 
some form of storage-reservoir. The other is that of continuous and 
d'rect pumping, in which the pump is operated at a speed just sufficient 
to supply the demand for water. 

From what has already been stated it will be seen that for water- 
supply purposes there are great variations in the demands for water 
between the maximum and minimum consumption, and especially 
between minimum consumption and fire service. A pumping-plant for 
water-supply must be equal to the maximum demands unless the 
storage capacity is sufficient so that a uniform rate of pumping can be 
maintained and any unusual demand can be cared for by the stored 
supply. If the pumps are of sufficient capacity for maximum demands, 
their average rate of work will usually be very low, and low efficiency 
will often result (see Art. 669). In pumping into a storage-reservoir, 
the pumps can be operated at their most efficient rate regardless of 
consumption, which renders their operation much more economical. 
The direct-pressure system involves attendance night and day, while 
when pumping to a reservoir, night work, and consequently perhaps 
half the labor, can be saved in small plants. In large plants the 
pumps must be run night and day in any event. The variation of 
consumption in large plants is comparatively small, and it does not 
therefore greatly affect the economy of operation. The pumps can be 
run at or near their most efficient rate, and for great changes in con¬ 
sumption the variation in quantity can be cared for by starting or 
stopping some of the reserve machinery. 

The quantity of water used in different cities for domestic consump¬ 
tion varies in the United States from 30 to 300 gallons per capita, 
according to conditions previously discussed. The quantity of water 
which will be needed at the maximum rate of consumption has already 
been considered. For fire service the number of fire-streams which 
should be estimated for any community depends largely on the character 
and nature of the community to be protected. The formula of Mr. E. 
Kuichling, Mem. Am. Soc. C. E., for the number of fire-streams which 
should be provided for any community is as follows: 


COMPARISON OF ECONOMY OF DIFFERENT DESIGNS. 


627 


Number of streams = 2.8 Vx\ 

in which = the population of the community in thousands (see 
Chapter II). 

694. Comparison of the Economy of Different Designs. —The first cost 
of a pumping-plant, and the fuel cost, are not the only considerations 
in its selection. There must also be considered all other costs in con¬ 
nection with the plant, including all expenses involved in the original 
installation and all expenses entailed in its operation and maintenance. 
For example, one pumping plant may require a more expensive foun¬ 
dation, or a larger building, and the interest and sinking fund on such 
-additional cost may more than offset any saving due to higher duty or 
greater efficiency. 

Simplicity of arrangement is also very desirable. Complication in 
construction is objectionable because it necessarily entails greater 
expense in repairs and maintenance, and greater probability of acci¬ 
dents to the installation. 

Pumping-machinery for fire service and for public water-supplies 
must be so installed as to be practically free from the danger of a failure 
in the service. This is accomplished either by the duplication of the 
plant as a whole or in part, or the storage of water under pressure, or 
often by both. In important cases simplicity in design and the conse¬ 
quent positive assurance of successful operation at all times may out¬ 
weigh economy in operation. 

These points cannot be given a definite value or basis of compari¬ 
son, except when all facts regarding the demands on an installation 
are known. 

The comparative financial relations of various plants can be made 


on the following basis: 

Interest on cost of installation. $ 

Annual cost of operation: 

Labor. . . $ . .. 


Fuel. 

Oil. 

Waste. 

Light. 

Miscellaneous. 

Total. 

Annual cost of maintenance and repairs. . . . 
Annual debit to sinking fund.. 

Total relative cost of plant. 
























628 


PUMPING-MA CHINEE V. 


695. Example .—The following is an example of the application of 
the above principles to a small pumping-plant which was to be installed 
to replace a plant already in use. The plant in use consisted of two 
double-acting direct steam pumps raising water from deep bore-holes 
from a depth of 160 feet below the surface into a reservoir at the sur¬ 
face. From this reservoir the water was pumped into the water-mains 
against about 45 pounds direct pressure. It became necessary to 
increase the water-supply, which was to be secured from deep wells as 
before. To accomplish this various plans were investigated. 

The cost of operation of the old plant was excessive. This was 
due to the fact that the pumps used were all extravagant of steam, and 
the pump which was pumping into the mains had to operate constantly 
and at only about one-fifth its capacity. To reduce the cost of operation 
a stand-tower was proposed, and its cost was included in all estimates 
made. A new deep well was also included in the cost of each plant. 

The plans investigated were: 

1. The enlargement of the old plant, including, besides the stand- 
tower and deep well, a deep-well pump and a direct-acting duplex 
steam-pump. 

2. The old system enlarged as above, but substituting steam-engines 
and power deep-well pumps for the direct-acting deep-well pumps. 

3. Using deep-well power-pumps and steam-engines, and pumping 
directly into mains and stand-tower without using duplex steam-pump. 

4. Substituting the air-lift system for the deep-well pumps, the esti¬ 
mate to include compressor air-lift apparatus and new duplex steam- 
pump. 

5. Sinking shaft 150 feet deep and installing suction-pump within 
reach of the water to force the water directly into mains and stand¬ 
pipes. Estimate to include shaft and pump. 

Table No. 93 gives the estimate of probable results made on the 
various plants outlined above. 

From the showing in the table under a , b, and c, as well as for 
many other reasons, it was decided that the shaft system was the best 
system to adopt. 

Various classes of pumps could be used with the shaft system. 
Table No. 93 (d) gives an estimate of the relative cost and economy of 
various types. 

This plant was intended to have a capacity for fire service of 
1,000,000 gallons per day, but an average of about 200,000 gallons 
per day would be used for domestic purposes. From the above table 
it will be observed that at the rate of pumping of 200,000 gallons per 


COMPARISON OP ECONOMY OF DIFFERENT DESIGNS. 629 

TABLE NO. 93 . 

EXAMPLE OF A FINANCIAL COMPARISON FOR A PUMPING-PLANT. 


(a) Estimated Cost of Operation and Relative Expense . 


System. 

Engineers 

Repairs. 

Oil. 

Fuel. 

Total. 

Saving 
over Pres¬ 
ent Cost. 

Present system. 

$1440 

$362 

$33 

$2041 

$3876 


Present system enlarged. 

Present system with power 

1440 

400 

35 

1400 

3475 

$401 

deep-well pumps. 

I440 

300 

35 

1250 

3025 

851 

Direct deeo-well pumps. 

1440 

350 

30 

800 

2620 

1256 

Air-lift system. 

1440 

IOO 

25 

1400 

2965 

911 

Shaft system.. 

I44O 

IOO 

25 

500 

2065 

l8ll 


( b ) Amount of Investment Warranted by Saving Effected. 


System. 

Estimated 

Cost. 

Present svstem. 


Present system enlarged. 

$17000 

Present system with power 


deep-well pumps. 

20000 

Direct deep-well pumps. 

21500 

Air-lift system. 

22000 

Shaft system. 

22000 


Cost of 

Saving 

Saving Capitalized at 

Operation. 

per Year. 

6 % 

5 # 

$3876 

3475 

$401 

$6683 

$8020 

3025 

851 

14185 

17020 

2620 

1256 

20966 

25120 

2965 

911 

15185 

18220 

2065 

l8ll 

3OI83 

36HO 


(c) Financial Comparison. 


System. 

Interest on 
Cost of 
Installation 
at 5%. 

Annual Cost 
of Operation. 

Annual Cost 
of Repairs, 
etc. 

Sinking 

Fund. 

Total Cost 
per An num 

Present system enlarged. 

Present system with power 

$850 

$3075 

$400 

$1015 

$5340 

deep-well pumps. 

IOOO 

2725 

300 

1235 

5260 

Direct deep-well pumps. 

1075 

2270 

350 

1275 

4970 

Air-lift system. 

I IOO 

2865 

IOO 

1325 

5390 

Shaft system. 

1250 

1965 

IOO 

1085 

4400 


(d) Cost of Operating Various Types of Pumps for Shaft Systems. 


Class of Pump. 

Cost. 

Duty, 
1000 lbs. 
Steam. 

Estimated Cost of Fuel per Year on 
Rates in Gallons. 

200,000 Gals. 

500,000 Gals. 

1,000,000 Gals. 

Engine and power-pump 

Corliss geared pump.. . 

High-duty pump. 

Dif. 

$4000 

$2500 

6500 

5500 

11000 

Int. on 
Dif. at 
6 %. 

$150 

330 

Lbs. 

50 

75 

IOO 

Dif. 

$350 

$83 

267 

92 

175 

Dif. 

$875 

$208 

667 

230 

437 

Dif. 

$1750 

$415 

1335 

460 

875 




































































































630 


PUMPING-MA CHINER Y. 


day the difference in the cost of fuel between pumps of types I and 2 
is estimated at $83 per year, or less than the interest on the difference 
in the cost between the two engines. The cheapest of the above 
pumps is therefore the mcst economical for these conditions. If the 
rate of pumping were 500,000 gallons per day, the second pump in the 
above table would be most economical, and if the rate were 1,000,000 
gallons, the third and most expensive pump would be best. 

The various other conditions which have heretofore been men¬ 
tioned, and which are often as important as the financial conditions, 
were carefully considered. The object was and always should be to- 
secure the best possible pumping-plant after having carefully examined 
the question of safety and security in construction, operation, and 
maintenance, and economy in the first cost, in operation and in 
maintenance. 


LITERATURE. 

The following list contains the titles of a few of the most useful books 
and papers relating to pumping-machinery. 


BOOKS AND MONOGRAPHS. 

1. Barr. Pumping-machinery. Philadelphia, 1893. 

2. Behr. Mine-drainage Pumps, etc. Published by the California State 

Mining Bureau. 

3. Buchetti. Les Pompes Centrifuges et Rotatives. Paris, 1895. 

4. Hartman. Die Pumpen. Berlin, 1889. 

5. Poillon. Traite Theoretique et Pratique des Pompes et Machines a 

elever les Eaux. Paris. 

6. Richards. Centrifugal Pumps. Published by Industrial Pub. Co. 

7. Weisbach & Herrmann. Mechanics of Pumping-machinery. New York 

1897. 

8. Davey. Pumping-machinery. London, 1900. 

PERIODICAL LITERATURE. 

1. Kent. Pumps and Pumping-machinery. Mechanics , Sept. \^o et seq. 

2. The Screw Pumping-engine of the Milwaukee Elushing-tunnel. Eng* 

News , 1890, xxi. p. 218. 

3. The Air-lift Pump. Eng. News, 1893, xxix. p. 541. 

4. Dean. Recent Practice in Pumping-engines. Jour. New. Eng. W. W„ 

Assn., 1893, vi. p. 85. 

5. The Leavitt High-duty Pumping-engine, Boston. Eng. News, 1894, 

xxxii. p. 176. 

6 . Raising Water by the Air-lift. Eng. Record, 1895, xxxi. p. 363 et seq. 

7 . Test of the Detroit Pumping-engine (Allis). Description of plant and 

test. Eng, Record , 1895, xxxii. p. 477. 


LI TER A TURE. 63 1 

8. Leavitt. A Few Examples of High-grade Pumping-engines. Jour. New 

Eng. W. W. Assn., 1895, ix. p. 163. 

9. Mead. The DeKalb Electrical Pumping-plant. Jour. Assn. Eng. Soc., 

1895, xv. p. 83. 

10. Miinzel. Wasserversorgung mit Gas-, Benzin- und Petroleummotoren- 

betrieb. Zeit. d. Ver. Deutsch. Ing., 1895, xxxix. p. 303; Eng\ 
Record, 1895, xxxn. p, 4. 

11. Mead. The Hydraulic Ram. Eleventh Report, Ill. Soc. Eng. and 

Surv., p. 50. 

12. Some Recent Installations of Power-pumps in Small Water-works. Eng % 

News, 1896, xxxv. p. 349. 

13. Hague. An Electrical Pumping-plant. Jour. New Eng. W. W. Assn., 

1896, x. p. 184. 

14* Newcomb. Water-works Machinery. Cassier's Magazine, 1896, x. 
p. 168. 

15. Johnson. Limitations of the Air-lift Pump. Eng. News, 1897, xxxvii. 

p. 250. 

16. Test of Air-lift at Rockford, Ill. Eng. News, 1897, xxxvii. p. 140. 

17. Richards. The Design of Centrifugal Pumps. Eng. News, 1897, 

xxxviii. p. 75. 

18. Johnson. Deep-well Pumping. Jour. West. Soc. Pmgrs., 1897, 11. 

p. 169. 

19. Hood. Test of Pumps and Water-lifts. Water-supply and Irrigation 

Paper, U. S. Geol. Survey, No. 14, 1898. 

20. Hague. Triple-expansion Engine at Ogdensburg, N. Y. Eng. News , 

1898, xl. p. 322. 

21. Johnson, A New Continuous-flow Deep-well Pump. Eng. News, 1898, 

xxxix. p. 34. 

22. Richards. Recent Improvements in Centrifugal Pumps. Eng . News y 

1898, xl. p. 340. 

23. Marston. The Iowa Agricultural College Deep Well and Pump, Ames, 

la. Eng. Record, 1898, xxxvii. p. 387. Efficiencies of various 
deep-well pumps given. 

24. Maury. Supplemental Pumping-plant of the Peoria Water Company, 

Peoria, Ill. Eng. News, 1898,'xxxix. p. 19. Centrifugal pumps 
operated by water-motors. 

25. Hague. Pumping-engines Driven by Water-power. Eng. News, 1899, 

XLII. p 6. 

26. Reynolds. Present Pumping-engine Practice of the Edward P. Allis Co, 

Compared with that of Twenty-five Years Ago. Jour. New Eng. 
W. W. Assn., 1899, xm. p. 172. 

27. Coffin. The Application of Gas-, Gasoline-, and Oil-engines to Pump¬ 

ing-machinery. Jour, New Eng. W. W. Assn., 1899, xm. p. 206; 
Eng. Record, 1899, xxxix. p. 79. 

28. Barrus. The Possibilities of Economy in Pumping-engines. Jour. New 

Eng. W. W. Assn., 1899, xm. p. 163. 

29. A Gasoline Pumping-plant for the Water-works of Toms River, N. J, 

Eng. News, 1899, xli. p. 197. 

30. The New Rockford Pumping-plant. Eng. Record, 1899, xxxix. p. 352. 

31. Mead. The Mechanics of Suction and Suction-pipes. Jour. West. Soc. 

Eng., 1899, iv. p. 12. 


632 P UMPING-MA CHINER Y. 

32. Mead. Deep-well Pumping-machinery. Proceedings Am. W. W. Assn., 

1899. 

33. Rix. Pumping by Compressed Air. Jour. Assoc. Eng. Soc., 1900, xxv. 

P- * 73 - 

34. Cooley. Test of a Fifteen-million-gallon High-duty Pumping-engine at 

Grand Rapids, Mich. Trans. Am. Soc. M. E., 1900, xxi, Paper 
No. 863. 

35. Goss. Test of the Snow Pumping-engine at Indianapolis. Trans. Am. 

Soc. M. E., 1900, xxi, Paper No. 854. 

36. Mead. The New Water-supply Plant at Rockford, Ill. Trans. low? 

Eng. Soc., 1901. 



! 




S 





CHAPTER XXVII. 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 

696. Office.—The forms of reservoirs to be here treated include all 
those which are interpolated at any point in a system between the 
original source and the consumer. The particular function of these 
reservoirs differs considerably according to circumstances, but in 
general they are inserted to furnish elasticity to the distributing system, 
that is, to enable the different portions to be more or less independent 
of each other in their operation. 

Such independence of action is desirable from the standpoint of 
economy and safety, and in many cases is of importance with respect 
to the quality of the water. For example, where the water is brought 
from the source through a long conduit, a distributing or equalizing 
reservoir will enable the conduit to be operated at a comparatively 
uniform rate and hence to be made of minimum size. Likewise such 
a reservoir will make it possible to reduce the capacity of pumps, or 
filters, or other similar works, and to operate them more uniformly and 
economically; or in the case of small works to operate the pumps at full 
capacity for a portion of the day only. In the case of a ground-water 
supply a small reservoir will greatly increase the capacity of the source 
by making the demand more uniform. Again, in a large distributing 
system, several reservoirs placed at different points will effect con¬ 
siderable economy in the size of the pipe system. 

As a measure of safety against the interruption of the supply from 
accidents to conduit or machinery, distributing-reservoirs are of great 
value; or, looked at in another way, additional safety against inter¬ 
ruption may often be obtained much more cheaply by this means than 
by duplication. 

With respect to the quality of the water a reservoir is often of great 
advantage, as pointed out on page 402, by affording opportunity for 
sedimentation and also by making it possible to avoid taking water 
from streams during periods of great turbidity. 

Small reservoirs are required also for convenience in operation, such 

^33 


634 * DISTRIBUTING AND EQUALIZING RESERVOIRS. 


as receiving-reservoirs at the terminals of conduits, small reservoirs 
for regulating the pressure at intermediate points, and similar reservoirs 
or air-chambers at pumping-stations for equalizing the action of the 
pumps. 

In all cases the purpose of the reservoirs here considered is to 
afford elasticity of operation. 

697. Kinds of Reservoirs.—In discussing forms of construction, 
reservoirs may be classified, according to the material employed, into 
(1) earthen reservoirs, (2) masonry reservoirs, (3) iron or steel reser¬ 
voirs, and (4) wooden reservoirs. The first two kinds can con¬ 
veniently be considered together, as the two materials are very often 
combined in the same structure. The last two will also be treated 
under the general title of stand-pipes and tanks. 

When the reservoir does not need to be elevated above the natural 
surface, the most economical form, and the usual one for large capaci¬ 
ties, is the open reservoir with earthen embankments. The storage of 
surface-waters in such reservoirs does not usually affect their quality, 
especially if they have previously been stored in large impounding- 
reservoirs; but in the case of ground-waters, or filtered surface-waters, 
it is usually desirable that they be stored in closed reservoirs. Such 
reservoirs are usually built with masonry walls and covers, partly in 
excavation and partly above the surface. If a reservoir requires to 
be considerably elevated, a Steel stand-pipe or a tank of wood or steel 
is usually employed. A few large reservoirs have also been con¬ 
structed of masonry that have extended to a considerable height above 
the ground. 

698. Capacity—The purpose of a reservoir of the kind here con¬ 
sidered being chiefly a matter of economy and safety, the capacity for 
which it should be designed is not subject to a rigid set of rules, but 
depends entirely upon local circumstances. It may be wise, and good 
economy, for one city to have a reservoir capacity equal to 8 or 10 
days’ supply, while for a town located on a level plain it may be best 
to dispense with a reservoir and rely entirely upon reserve machinery. 
In determining the proper capacity, the cost of the reservoir must 
therefore be balanced against the benefit derived therefrom in safety 
and in the reduced expense for other structures and reduced cost of 
operation. 

This question is conveniently considered in three parts: (1) the 
capacity necessary only to equalize the demand for a single day; (2) a 
capacity greater than this to provide additional safety or economy; (3) 
a capacity less than this where reservoirs become very expensive. 






CAPACITY OF PESERVOIRS . 


635 


(1) In Chapter II, page 30, are given several curves showing the 
hourly variations in consumption throughout the day. Assuming the 
supply uniform, the accumulated deficiency during the hours when the 
rate of consumption is greater than an average would be, for New York 
City, about 1.4 hours’ average supply; for Rochester, 2.5 hours; for 
Binghamton, 1.8 hours; for Des Moines, 3.7 hours; for Rockford, 1.7 
hours; and for Rock Island, about 1.1 hours. The higher the con¬ 
sumption the less the variation and hence the less the required storage 
as measured by the number of hours’ average supply. To equalize the 
demand on any particular day will then ordinarily require a storage 
capacity of from 1.5 to 3 hours’ average consumption for the day in 
question, varying much according to local conditions. Assuming the 
same variation on the day of maximum consumption, and taking the 
maximum daily consumption at 150 per cent of the average, the 
required storage to equalize the demand on any day will be equal to 
1.5 times the above figures, or 2.2 to 4.5 hours’ consumption taken as 
the yearly average. 

The quantity thus determined is sufficient only to equalize the 
demand during any single day, but does not provide for the variations 
in daily consumption. These must be met by varying the supply from 
pumps or conduits or other works. 

In addition to the above capacity, the fire consumption for a single 
fire must be provided for. The maximum rate of fire consumption is 
given on page 31. According to Freeman, a supply of 6 hours for the 
full number of streams is a sufficient provision for fire. For small 
towns and villages 3 or 4 hours’ supply at the maximum rate would in 
many cases be ample. The amount required for fires will, for exam¬ 
ple, be equivalent to about one day’s consumption for a population of 
5000, and about 6 hours’ consumption for a population of 100,000, 
assuming an average consumption of 100 gallons per capita. 

The capacity as here determined is the minimum desirable, where 
uniformity of operation is important for at least a day at a time; as, for 
example, for the clear-water reservoir of a filter system, or the storage- 
reservoir of a ground-water supply. It is also the minimum desirable 
size for the distributing-reservoir of a gravity or a large pumping 
system, and is less than would be used except where the cost of con¬ 
struction is very high. In the case of small towns where it becomes a 
consideration to operate the pumps but a portion of the day, the 
capacity must be made sufficient to furnish water during the hours when 
the pumps are idle, and in addition a reserve for fire extinguishment. 

( 2 ) With a capacity equal to that determined under (1), provision 


636 DISTRIBUTING AND EQUALIZING RESERVOIRS. 

for interruption of the supply for repairs would have to be made by the 
duplication of conduits, by reserve pumps, etc. The expense of such 
duplication may, however, be largely or wholly avoided by increasing 
the capacity of the reservoir. The best size of a reservoir depends then 
upon the time required for repairs, and upon its cost as. compared with 
the expense of duplication. Where it is possible to construct an inex¬ 
pensive open reservoir at a suitable elevation and in a good location it 
should be given a capacity of several days’ supply. In practice the 
capacity of such reservoirs varies from 2 or 3 days’ supply up to 8 or 10 
days, and occasionally more. Where water is conveyed in a long 
conduit the larger capacity is desirable in order to avoid all danger of 
interruption from accidents. In a purely pumping system a very large 
reservoir is not so necessary, but having it, the amount of reserve power 
may be reduced to a minimum. 

A reservoir of the kind here considered may be an elevated dis¬ 
tributing-reservoir, or a low receiving-reservoir from which the water 
may be pumped, according to the local conditions. 

(3) Where, owing to the topography, it becomes necessary to 
artificially elevate a reservoir in the form of a stand-pipe or elevated 
tank, the expense of construction becomes so great that the economical 
capacity is usually less than that mentioned under (1). The best 
capacity in this case depends much upon the size of the city. For large 
cities it is hardly practicable to provide much storage by means of 
artificially elevated reservoirs, the small stand-pipes which are often 
used in such cases serving merely to equalize the action of the pumps. 
In large cities the variations in demand occur more gradually than in 
small cities; the fire consumption is also of less relative amount, and 
with the large number of pumps in use their operation can be more 
easily varied to suit the consumption. The percentage of necessary 
reserve power is also much less than in small cities where the number 
of pumps is small. 

In small cities (up to a population of 50,000 or more) it is desirable 
to provide a small storage even at considerable cost, as a measure of 
safety and economy. The fire rate is here the principal consideration, 
and the minimum capacity should be such as to provide water at the 
maximum fire rate for a sufficient length of time to enable the pumping- 
station to respond with ease and certainty. This is ordinarily taken as 
about one hour. Beyond this it will usually be desirable to add to the 
capacity enough to equalize the ordinary flow over several hours of the 
clay, or, in the case of small works, to enable the pumping to be done 
by operating a part of the day only. The capacity beyond this mini- 


LOCATION. 


637 


mum one-hour’s fire consumption depends largely upon the cost of the 
tank and cost of pumping. If the tank can be placed on a natural 
elevation so as to reduce the height of construction, the capacity may 
approach that mentioned in (1) and thus reduce the amount of reserve 
power for fire purposes to a low figure. If the ground is level, the cost 
will be high and the capacity correspondingly low. 

699. Location.—The location of an elevated reservoir is governed 
in the first place by the topography, and the choice of location is there¬ 
fore often very limited. In general a distributing-reservoir should be 
located as centrally as possible with respect to the district to be served,, 
as this will insure the most uniform and the highest pressures and will 
give the smallest size of main and branches. The best arrangement is 
to have several reservoirs serving as many districts, but this is seldom 
practicable except in very large cities, the number being usually limited 
to one or two. 

(a). The Single Reservoir .—In a gravity system the conduit is 
terminated at a reservoir, and if this reservoir is centrally located a 
longer conduit will be required than if it be placed near one side of the 
system. A proper balance must be struck between the two extremes. 
In a pumping system the pumps are usually located near one side of the 
city, and the reservoir is placed either in the vicinity of the pumps or 
at a more remote point in the system. In the first case all the water 
is usually passed through the reservoir, and the action of the pumps is 
very steady and uniform. In the second case a main usually leads to 
the reservoir from some point of the distributing system. The pumps 
force water directly into the system, and the reservoir takes only the 
surplus at times of low consumption and distributes it at times of high 
consumption. Certain portions of the area are thus served direct, and 
others are served from the reservoir. With this arrangement a more 

uniform pressure will be maintained 
in the mains, but the operation of the 
pumps will not be as uniform. The 
conditions are illustrated diagrammat- 
ically in Fig. 194. Here P is the 
pumping-station, R is the reservoir, 
and AB the town to Ije served. 
During the night, water will flow into 
the reservoir, and the hydraulic gradient will be the line CR, say. 
During the day when the consumption is greater than the pumpage the 
reservoir will supply the deficiency, and water will flow to some point 
E from both directions, giving a pressure-line CDR. With the reser- 





638 DISTRIBUTING AND EQUALIZING RESERVOIRS. 

voir located at C the gradient will be a line CD' , steeper than CD if 
the size of pipes remains the same. To give as great average pressures 
in this case as in the other arrangement will require larger pipes except 
lin the immediate vicinity of R. 

( b ). Two or More Reservoirs. —Where two reservoirs are con¬ 
structed, the best arrangement would be to 
locate one near the pumps, or on the side 
of the town where the conduit enters, and 
the second near the opposite side of the sys¬ 
tem ; and where several can be built this 
scheme can be duplicated if the topography 
admits of it. An instructive example of 
such an arrangement is that of the reser¬ 
voir system for the supply from the Canal 
de l’Ourcq, Paris, illustrated in Fig. 195.* 

This arrangement is especially applic- Fig. 195. — Reservoir System, 
able to a city located in a river valley. Paris. 

700. Elevation.—The proper elevation of a reservoir depends on the 
required pressure in the mains, -a subject fully discussed in Chapter 
XXVIII. Where more than one zone of pressure is employed it will 
usually be possible to find sites for reservoirs to serve all but the highest 
zone. The latter may then be operated without a reservoir, or with a 
tank or stand-pipe. 

EARTHEN AND MASONRY RESERVOIRS. 

701. Form and Arrangement—Earthen reservoirs are usually con¬ 
structed partly by excavation and partly by the building up of embank¬ 
ments. If masonry walls are used in place of embankments, or as 
interior linings, the reservoir may be called a masonry reservoir. 

When not limited by other considerations, the location and elevation 
of the bottom is so chosen as to secure the most economical relation 
between excavation and filling, which relation depends much upon the 
ease with which material suitable for embankments can be obtained. 
For single reservoirs the form most economical of material is the cir¬ 
cular, but tor large reservoirs the rectangular form is more convenient 
to construct and requires less land area, and except when the topog¬ 
raphy favors an irregular outline, or where the reservoir is small, it is 
the form usually adopted. 



* Bechmann, p. 367. 







EARTHEN AND MASONRY RESERVOIRS. 


639 


Where a town is served by a single reservoir it is desirable to divide 
this reservoir into two basins in order that one basin may be in use at 
all times. This is quite necessary where cleaning must be done at fre¬ 
quent intervals, and it may be advisable in such a case to subdivide the 
reservoir still farther, as in the construction of settling-basins. 

For a single rectangular basin the square is evidently the most 
economical form. Where a reservoir is divided into two or more parts 
by interior embankments or walls, the economical proportions will be 
somewhat different from those suitable for a single basin. The best 
proportions may readily be determined by trial estimates, but where 
the embankments are of uniform height the general formula derived in 
the discussion relating to settling-basins is applicable. (See page 

4 H-) 

702, Depth.—The most economical depth is again a matter that is 
in any case easily determined by trial. It will, however, be useful to 
determine by analysis approximately the effect of various elements on 
the depth. Assuming a reservoir square in plan, let x = length of one 
side; h — depth; Q = given capacity; and c — cost per unit area 
of all that portion whose cost is proportional to the area, such as land, 
reservoir lining, cover, etc. The cost of wall or embankment will vary 
approximately as h'\ or will be equal to c'h 2 , where c' is a constant. 
The total cost will then be 


C = 4,-r^Vz 2 -[- cx % 



But Q — hx 2 , or x = \J whence, substituting in (1), we have 



Differentiating with respect to h, equating to zero, etc., we find that 
for a minimum C 



The economical depth is therefore proportional to the fifth root of Q, 
and hence it should vary but little for considerable variations in 

/ xc 

capacity. Since Q = hx\ we have, from eq. (3), li = y gp, that is, 

h is proportional to From eq. (3) we also see that as the cost 

per unit area increases from any cause, h should also increase, but 
only in the proportion of c\ In practice the depths vary from 12 to 






640 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


18 feet, for small covered reservoirs holding one million gallons or less, 
to 25, 30, or 35 feet, for open reservoirs holding 50 or 100 millions, 
depending upon local circumstances. With a fixed bottom elevation 
it is to be noted that the lift of the pumps increases with increased 
depth, which fact would tend to reduce the economical depth; also 
that shallow reservoirs give a less variable pressure in the distributing 
system. On the other hand too shallow reservoirs favor higher tem¬ 
peratures and increased vegetable growth, and are thus disadvantageous. 

703. Embankment Construction.—The construction of the embank¬ 
ment is based on the same principles as discussed in Chapter XVI, but 
the conditions are somewhat different from those obtaining with im- 
pounding-reservoirs. Distributing-reservoirs are relatively expensive 
structures and are usually located in populous districts and so need to 
be particularly impervious. No porous form of embankment is per¬ 
missible. In this case also the foundation is frequently pervious and 
the embankment cannot be connected with an impervious stratum 
below. Under such conditions it is necessary to construct a water¬ 
tight lining over the entire area, and to carefully connect it with the 
water-tight portion of the embankment. Where a lining is not neces¬ 
sary to secur imperviousness, one is usually put in to facilitate the 
cleaning of the reservoir. 

According to circumstances the entire embankment may be imper¬ 
vious, or imperviousness may be secured by a puddle or concrete core, 
or by a layer of puddle placed near the face. The same objections are 
made to puddle cores as in the case of high embankments, but with 
perhaps less force. A puddle wall near the face, Fig. 196,* is readily 


"-•CU - 1 



Fig. 196. —Section of Reservoir Embankment, Pittsburg. 

connected with the bottom lining, and in this case requires* less 
material than when placed as a core as in Fig. 197.I' It gives a less 
firm base for the pavement, however, than coarser earth, and when the 
water is drawn down there is more danger of slips, such as have 

* See Eng. Record , 1897, xxxvi. p. 54. 

\ See Eng. News , 1891, xxxvi. p. 78. 















LININGS OF EARTHEN RESERVOIRS. 641 

occurred in several instances. To avoid this, the paving should be 
placed on a layer of broken stone and have a good support at the base, 
somewhat as shown in the two sections here illustrated. 

To protect the puddle from frost action it is well to place it at some 
depth below the surface as in Fig. 196. An embankment with both a 
puddle core and face is shown in Fig. 77, page 340. 

The corners of all embankments should be rounded in order to 
admit of convenient working with rollers. If it becomes necessary to 



Fig. 197. —Section of Reservoir Embankment, Brooklyn. 

support the embankment on the outside at any point by a retaining 
wall, such wall should be made of a strength equivalent to the portion 
of the embankment removed and should not be made impervious. 

704. Linings of Earthen Reservoirs. —The most common form of 
lining consists of about ij to 2 feet of puddle protected by a layer of 
concrete, brick, or stone paving, or sometimes only by gravel. On 
the slopes the concrete is usually covered with paving or replaced 
entirely by it, experience showing that unprotected concrete is apt to 
be injured by ice. Various methods of construction are illustrated in 
Chapter XVI. Fig. 72, page 331, illustrates a case where the natural 
material was impervious and a concrete floor was all that was needed. 
A layer of paving-brick laid in cement makes a good finish for a con¬ 
crete lining which is to be frequently exposed. 

Concrete can be made impervious by plastering with cement 
mortar, neat or I to 1, but where it extends over large areas, cracks 
will form, due to temperature changes and to settlement of embank¬ 
ments. To minimize this difficulty, concrete is often laid in blocks, 
with asphalt joints between. At Pittsburg the concrete was made in 
the proportions 1,2, and 4, and laid in blocks 9 inches thick and about 
7 feet square, with V-shaped joints of asphalt between, f inch wide at 
the bottom and £ inch at the top. The whole was laid on a puddle 
lining. The concrete was plastered with inch of Portland-cement 
mortar, 1 to 1. A similar process was used at Minneapolis, the con¬ 
crete being laid in 20-foot squares. At the Albany filter-beds the same 

















'O42 DISTRIBUTING AND EQUALIZING RESERVOIRS. 

plan was used, it being specified that the asphalt was to remain soft at 
freezing temperatures. At Payson Park reservoir, Cambridge, the 
core-wall was made of concrete and then plastered. It was connected 
to the concrete lining by means of a layer of 6 to 12 inches of concrete 
laid on the natural earth beneath the embankment. The lining was 
plastered with £ inch of Portland-cement mortar, i to i (Fig. 198). 



Fig. 198. —Payson Park Reservoir, Cambridge. 

If ground-water is met with, which is under considerable pressure, it 
will be necessary, in order to avoid rupture of the floor, to drain the 
soil beneath the lining. In some cases the ground-water has been 
permitted to enter the reservoir, when its head exceeds that in the 
reservoir, through flap-valves which will close when the difference of 
head is in the reverse direction. Drainage of the soil beneath the 
lining should be done with great caution, and especial care taken to 
.surround all drains with gravel and sand so graded in fineness as to 
effectually prevent the washing out of any of the material. Seepage- 
water is also sometimes taken care of by means of drains. 

705. Asphalt Linings .—Asphalt has for some time been extensively 
used for reservoir linings on the Pacific coast, and recently its use has 
become quite general. Compared to concrete it has the advantages of 
elasticity and greater imperviousness, both of which are of great 
importance in this connection. Another advantage in many cases is 
its cheapness. Its chief disadvantage is the effect of the sun in render¬ 
ing it more or less plastic and liable to creep if used on steep slopes. 
Its durability in water is also not fully determined. Great care and 
expert knowledge are required in determining the proper proportions 
of the various ingredients necessary to give good results. 

Asphalt, or bitumen, in its natural state exists in various degrees 
of purity and consistency from a hard bituminous limestone rock, con¬ 
taining comparatively little bitumen, to a nearly pure semiliquid 
bitumen. By selecting certain grades, or by mixing and heating, or 
adding limestone dust, etc., asphalts can be obtained which will become 
hard at various temperatures. The soft mixtures are adhesive, but will 














LININGS OF EARTHEN RESERVOIRS. 


643 

flow when exposed to the sun, while the harder mixtures are less 
adhesive. Hard asphalts are fluxed by mixing with natural soft 
asphalts, or with petroleum residuum. The former flux is considered 
the better for reservoir purposes. 

Asphalt is applied either alone, or in the form of asphaltic mortar 
or concrete, consisting of mixtures of asphalt with sand or broken stone. 
For rigidity and strength the broken stone mixture is to be preferred. 
Regarding the use of asphalt, the following is quoted from L. J. LeConte, 
M. Am. Soc. C. E., who has had much experience with this material: * 

“For the bottom and side slopes flatter than to 1 the best mixture is 
either asphalt mortar or asphalt concrete. It is the cheapest and best lining, 
and there is no danger of its crawling down the slopes. For steeper slopes, up 
to vertical faces, this kind of lining has been tried and found wanting in many 
respects. Under a hot summer sun it will creep down the faces in spite of 
all precautions. Steep slopes or vertical walls are now coated as follows: 
First , with a cold liquid asphalt paint, which has great penetrating and 
adhesive properties but is lacking in sun-proof qualities; second , with a heavy 
layer of ordinary burlap, which is tightly stretched and pressed into this 
liquid asphalt paint; third , with a heavy outside coat of hard asphalt paint, 
put on boiling-hot. This constitutes the weather coat, and is hard, tough, 
and resists the hot summer sun admirably. Wherever this lining has been 
used, no signs of creeping have developed even on smooth vertical faces. 
Hard asphalt paint is lacking in adhesive qualities and consequently cannot 
be placed directly on the slopes. The contract price of this lining has varied 
from 12 to 16 cents per square foot, depending upon local conditions.” The 
second coating referred to is usually laid at a temperature of from 300 to 400 
degrees. 

When the earth is firm and compact, asphalt linings can be placed 
directly upon it, and have frequently been so placed. Considerable 
settlement has in some cases taken place without cracking the lining, 
but this cannot, of course, be relied upon. 

In relining the Queen Lane reservoir at Philadelphia, with the old 
concrete lining left in place, asphalt concrete 2 inches thick was 
used for the floor and a double layer of asphalt on the slopes, in a way 
essentially similar to that recommended above, with the exception that 
a priming coat of asphalt dissolved in benzine was first applied to all 
concrete surfaces of the old lining to insure good adhesion. The price 
was $1.15 per square yard for the bottom and $1.40 for the slopes. 
The slopes were furthermore lined with brick, laid flat in an outside 
priming coat of asphalt, to give protection from sun and ice. In the 
new settling-basins for the Cincinnati water-works the lining consists 
of concrete 6 inches, asphalt \ inch, brick 2 \ inches. 


* Trans. Am. Soc. C. E., 1896, xxxv. p. 94. 




644 DISTRIBUTING AND EQUALIZING RESERVOIRS. 

706. Reservoirs with Masonry Walls. —These occupy less space than 
earthen reservoirs, but are more expensive to construct. They are, 
however, often the best form for small reservoirs where space is limited, 
and are a suitable form in case covers are required. 

When the reservoir is excavated in firm earth or is backed by a 
well-compacted embankment, the earth serves to support the walls 
against water-pressure. They must then be designed to sustain the 
earth-pressure with reservoir empty. By adopting the circular form 
the masonry will resist largely by compression as a ring, and the 
dimensions can be considerably reduced below those required for a 
wall resisting by gravity alone. The relative resistance as a ring 
decreases as the square of the radius increases, but for reservoirs up to 
75 or 100 feet in diameter this element may be largely relied upon for 
support. Several small circular reservoirs have been built of diameters 
of 50 to 75 feet, with walls from 16 to 22 inches in thickness. 

The masonry may be of rubble, concrete, or brick, according to cir¬ 
cumstances. If exposed, a lining of paving-brick makes an excellent 
finish. It is needless to say that in all work of this character the 
greatest care should be taken to secure the best workmanship, particu¬ 
larly in the mixing and laying of concrete and the thorough filling of 
masonry joints with mortar, essentially as in dam construction. 

Imperviousness is usually secured in large masonry reservoirs by a 
layer of puddle placed back of the wall and thoroughly rammed, and 
the bottom lining is treated in a similar way. In small reservoirs more 
reliance is placed upon impervious masonry, made so by an asphalt 
coating, or, more commonly, by a coat of Portland-cement mortar, 
neat or 1 to 1, which it is well to finish by a brush-coat of neat 
cement. The latter method is more likely to be satisfactory with 
covered reservoirs, where the temperature changes are small, than with 
open reservoirs. 

While it is comparatively easy to secure imperviousness at the start 
by the use of cement, it is difficult to prevent the formation of slight 
cracks. These permit the water to find its way into the surrounding 
soil, and when the reservoir is quickly emptied this water exerts a back 
pressure on the walls and an upward pressure on the floor. It is also 
likely to injuriously affect the backing and the foundation. This con¬ 
tingency may be provided against by draining the backing outside and 
near the base of the walls, and the ground beneath the floor. In some 
large masonry reservoirs recently constructed in France, a double 
bottom was put in, with a large interior space from which all seepage 
is removed by drains. Drains also lead into these galleries from behind 


ARRANGEMENT OF PIPES , VALVES , ETC. 645 

the exterior walls. In this way water is prevented from soaking into 
and weakening the foundation (Fig. 204, page 652). 

In the case of covered reservoirs, the floor may be designed to resist 
the upward pressure due to ground-water by the use of inverted groined 
arches, held down by the piers supporting the roof. 

The foundation for the walls should be broad enough to reduce 
settlement to very small limits, and as a further precaution against cracks 
the floor-lining should be constructed after the walls are complete, but 
should be thoroughly bonded thereto. Junctions between floors and 
walls are preferably made curved. 

707. Arrangement of Pipes, Valves, etc. —Distributing-reservoirs are 
usually provided with separate inlet- and outlet-pipes, located prefer¬ 
ably on different sides of the reservoir in order to promote circulation 
of the water. In earthen reservoirs these are constructed in the same 
manner as described in Chapter XVI. A by-pass should be provided 
to enable the reservoir to be cut out at any time. The gate- or valve- 
chamber will vary in design from a single vault placed over a gate- 
valve, to an elaborate structure provided with screens and arrangements 
for drawing water from different levels, as in the Syracuse reservoir 
(page 345), according to the size of reservoir and the necessities of 
the case. To prevent flooding of the embankments from carelessness 
in operation, an overflow must be provided. This is merely an open- 
ended pipe or short weir, admitting water to the gate-chamber or to a 
manhole, whence it is conducted away by a drain-pipe laid through the 
embankment. To facilitate draining and cleaning, a waste-pipe should 
lead from a low point in the floor of the reservoir. These details are 
illustrated in Fig. 199 and in Figs. 77 to 81 of Chapter XVI. 

Where the reservoir serves merely as an equalizing-reservoir, 
receiving only the surplus water from the distributing system, a single 
pipe will serve for both inlet and outlet. Circulation of the water can 
be secured by extending the pipe to the center, or beyond, and there 
placing a flap-valve through which water is admitted to the reservoir. 
A branch pipe opening near the side of the reservoir can then be made 
to act as an outlet-pipe only, by the use of a check-valve opening out¬ 
wards. 

For reservoirs serving partly or wholly as settling-reservoirs, the 
adjustable outlet-pipe shown in Fig. 199 is advantageous in enabling 
the water to be drawn off at all times from near the surface. The 
pivoted arm is provided with a float and screen, and in some works, 
provision is made to draw it to any desired depth by means of a chain 

and windlass. 


640 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


In open masonry reservoirs gate-chambers are conveniently built 
in connection with the reservoir wall. In covered reservoirs they are 
usually omitted, the valves being placed within the reservoir and 
operated from a suitable platform or from the outside. 



Galvanized Iron Tube So'inside Dia. 


Concrete, 


£l.4l£.5 ,r 


Bnoh 


Float 
tfinsidt via 
9b’Long 

& 

Brick: 


...eo'ii’ 


Brick. 


Floating Tube, 


4Q9.2$ 



hinge of Floating Tub©. 



Top View. 


Ocrivanhzd Ironrhs 'Wi*i‘L> 


TOpofWQtZr El 4340 
S'Cement.H 


£1.433.0 

STone-wL 


&W.0 Plank. W'WrouQtrtlron Pipe 
I Galvanized^ 



EL4I00 


Cross-Section. 

Fig. 199. —Outlet-pipe Details, Steubenville Reservoir. 

(From Engineering Record , vol. xxxvm.) 


708. Covered Reservoirs —In Chapter IX, page 170, the effect of 
storage on various classes of waters was discussed. It was there shown 
that ground-waters should be stored in covered reservoirs, for the reason 
that such waters usually contain sufficient quantities of plant-food to 
promote a luxuriant growth of vegetable organisms unless the light be 
excluded. Many cases have arisen of bad tastes and odors due to this 
cause which have been entirely removed by covering the reservoir, but 
the conditions are often so favorable for the growth of plants that con¬ 
siderable care must be taken to exclude all light. Filtered surface- 




























































































































COVERED RESERVOIRS. 


647 


waters should also as a rule be stored in covered reservoirs, since by 
the process of filtration they are rendered somewhat similar in nature 
to ground-waters. Where reservoirs are located in the densely popu¬ 
lated portions of cities, covers are also advisable, in order to exclude 
soot and dust. Distributing-reservoirs are almost universally covered 
in European works, and as the use of filtered supplies becomes more 
general in this country covered reservoirs will become more common. 

Covers are usually made of masonry, but wood has been used in a 
number of cases. It is much cheaper than masonry, but is much less 
durable and does not keep the water as cool in summer or wholly 
prevent freezing in winter. 

709. Wooden Covers. — A wooden cover for a large area may con¬ 
sist simply in a horizontal floor of boards, supported by a system of 
joists and girders resting on a series of wooden posts. No attempt 
need be made to exclude the rain. For small areas the covers can 
readily be made sloping, and this is a preferable arrangement. Covers 
for small circular reservoirs and large wells are conveniently made 
conical, with the rafters resting against the wall or supported on light 
trusses. An example of a wooden cover constructed over a large 
earthen reservoir is that at Quincy, Ill.* The posts are 6x6 inches, 
placed 14 and 18 feet apart. Upon these rest 6 X 6-inch girders which 
support 2 X 8-inch joists. The covering is composed of i-inch white- 
pine boards. The cost, exclusive of painting and of the brick piers for 
foundations, was 4 cents per square foot. The reservoir is 415 feet by 
317 feet by 26 feet deep. 

710. Masonry Covers. — Masonry covers consist usually of segmen¬ 
tal or elliptical masonry arches supported by small brick piers; or, for 
very small reservoirs, a dome may be used. Above the arches, about 
2 feet of earth is placed to prevent extreme variations of temperature 
and to protect the masonry, and embankments are constructed against 
the side walls to meet the covering above. The piers are spaced from 
10 to 15 feet apart, and are made from 1 to 2 feet square in cross-sec¬ 
tion, depending upon the span and weight of filling. As the loading 
is all dead load, a low factor of safety may be employed and piers and 
arches made relatively light. Much of the older construction is heavier 
than necessary. Table No. 94, by Coffin,* gives the dimensions and 
pressures for the piers of several covered reservoirs. 

The most common form of arch construction heretofore employed 

* Eng. News , 1898, xxxix. p. 373 * 

f From a very complete paper on covered reservoirs in Jour. Assn. Eng. Soc., 
1900, xxxiii. p. 1. 







648 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


TABLE NO. 94. 

DIMENSIONS OF AND PRESSURES ON PIERS OF COVERED RESERVOIRS (COFFIN). 


Reservoir. 

Height. 

Feet. 

Cross- 
section. 
Sq. Feet. 

Area of 
Tributary 
Roof 
Surface. 
Sq. Feet. 

Approx. 
Weight on 
Pier. 
Tons. 

Pressure 
on Pier. 
Tons per 
Sq. Foot. 

Newton. 

13-5 

2.78 

136 

32 

11 .5 

Brookline. 

17-5 

4.OO 

144 

26.5 

6.63 

Franklin. 

16.5 

I. OO 

90.5 

20 

20 

Ashland. 

5 -o 

4.00 

248 

54 

13-5 

Wellesley . 

12.25 

4.00 

196 

5i 

12.75 

Albany. 

7*50 

2.78 

187 

4i 

14-75 

Clinton. 

7.0 

4.OO 

210 

73 

19.50 

Proposed. 

7.0 

2. 78 

I96 

46 

16.55 


is that of cylindrical arches supported on lintel arches as shown in Fig. 
200. These lintel arches are made of the same width as the piers and 
usually of two rings of brick, with brick spandrel filling forming skew- 



Fig. 200.—Covered Reservoir, Waltham, Mass. 


backs for the covering arches. The latter are usually 8 inches thick, 
but have sometimes been made as light as 4 inches on a span of 1 1 
feet. Spandrel filling of concrete is added, and to prevent seepage the 
whole is plastered with cement or covered with a thin coat of asphalt. 
The earth filling is then placed and sodded. Rain-water can be 
excluded by suitable drains laid in gravel, or may be admitted to the 
reservoir through drain-pipes built in the masonry. 

Recently more attention has been paid to economy in the covering 
of reservoirs, and extensive use has been made of concrete for this pur¬ 
pose. The groined arch has also been used to a considerable extent, 
thus doing away with the lintel arches, and decreasing the amount of 
back-filling above. This method of construction is shown in Fig. 201 
which illustrates a covered filter at Ashland, Wis. 















































COVERED RESERVOIRS. 


649 

In this case elliptical groined arches of Hf-foot span and 3£-foot 
rise were used. The arch rings are about 5 inches thick and consist 
of two courses of brick laid flatwise in Portland cement. The spandrels 
are filled with concrete. Another example of the use of the groined 
arch is in the Albany filter illustrated on pages 438 and 448. Here the 
span is 12 feet and rise 2J feet. Concrete arches were used with a 
thickness at the crown of 6 inches. 

The stresses in groined arches are so complicated and uncertain 
that an analysis based on the assumption of simple arch action is of 



Fig. 201.—Covered Filter, Ashland, Wis. 
(From Trans. Am. Soc. C. E., Vol. xliii.) 


very little value. Where the masonry has considerable thickness over 
the pier it probably acts more as a cantilever than an arch. This was 
shown to be the case at the Albany filters, where the arches actually 
opened at the crown from the effects of temperature changes, the con¬ 
crete being so constructed as to give a line of weakness at this point. 
The economical proportions can best be determined by tests or from 
actual experience. The dimensions selected for the Albany filters 
have proven abundantly large, it being found entirely safe to drive a 
one-horse cart loaded with earth over any point of the cover. 

In Paris, Belgrand has constructed covers of concrete groined 
arches with a thickness of but 2.8 inches at the crown for a span of 









650 DISTRIBUTING AND EQUALIZING RESERVOIRS. 

13.3 feet, and 4.4 inches for a 20-foot span. The piers were from IQ 
to 17 feet high and 13 to 18 inches square.* 

Piers should be spread out at the base so as to distribute their load 
sufficiently to avoid practically all settlement, and the floor should be 
well bonded thereto. Where the foundation is soft, inverted groined 
arches may be used, thus distributing the weight over the entire area. 

The use of concrete-steel construction for reservoir vaulting has 
been suggested by several, and with low prices for steel it would doubt¬ 
less give considerable economy over the use of concrete alone. Prob¬ 
ably the simplest and cheapest form for this kind of vaulting would be 
a uniform covering of concrete and expanded metal, resting on piers 
which are spread out somewhat at the top. 

The cost of masonry covers has ranged from about 25 to 50 cents 
per square foot. The concrete cover of the Albany filters cost about 
28 cents, which represents the cost of concrete construction on a large 
scale and with economical proportions. 

711. Exterior Walls. — Reservoirs with earth embankments are 
occasionally covered with masonry vaulting, but the economy of earth 
slopes largely disappears in the covered reservoir, so that masonry walls 
are nearly always used. These walls must, of course, be designed 
with reference to the arch thrust. In practice the walls are usually 
made from 2 to feet thick at the top, and with an outside batter of 
1 in 10 and a vertical inside face. In circular reservoirs the arch thrust 
may be resisted by steel rings embedded in the masonry. In some of 
the more recent reservoirs constructed in Germany, the wall, instead of 
being vertical, has been modified to conform more closely to the 
resultant pressure of arch and earth, thus giving a more economical 
form. An extreme design of this character is illustrated in Fig. 202.f 



Fig. 202.—Small Reservoir at Vienna. 

P'ig. 203 illustrates a small covered reservoir at Leipsic, Germany, 
in which this feature is less prominent. 

Concrete naturally lends itself to such forms more readily than stone 

* See analysis of stresses in Coffin’s paper, also in paper by Metcalf in Trans. 
Am. Soc. C. E., 1900, xliii. p. 37. 

\ Zeit, d. Vereiti deutsch. Ing., 1898, xlii. p. 1059. 













COVERED RESERVOIRS. 6 5 I 

masonry. An important consideration in adopting - light curved sec¬ 
tions of concrete is the expense of the necessary molds. 

712. Masonry Reservoirs Above Ground. —Where no suitable eleva¬ 
tion can be found for a reservoir of the kind already considered it will 
be necessary to provide artificially the required elevation. Ordinarily 
a small elevated tank is made to suffice, but in the case of large cities 
served by long conduits it is desirable to have a larger storage 
capacity, and in a few instances this has been provided for by large 



Fig. 203.—Reservoir at Leipsic, Germany. 


masonry reservoirs. In these reservoirs the thickness of the walls is 
determined in the same way as for masonry dams. Sometimes earth 
embankments are thrown up around the walls to maintain the water at 
a lower temperature. Very interesting examples of high masonry 
reservoirs are furnished by those of Paris. The most remarkable 
perhaps is the Montmartre reservoir, which is four stories high, each of 
the upper three stories being used for different services. The lowest 
story is for the piping and for the drainage of water which leaks through 
the floor. Fig. 204 shows a section of this reservoir. Reservoirs of 
this class should receive careful architectural treatment and may be 
made fine monumental works. 

In repairing the inevitable cracks which appear in these large reser¬ 
voirs, the cracks are first cleaned out and then vulcanized rubber strips 
are cemented in with rubber cement, and the whole is covered with 
mortar.* 

713. Cost. —The cost of reservoirs varies of course greatly accord¬ 
ing to local conditions, kind of reservoir, and capacity. According to 
capacity the cost per unit will be less the larger the reservoir. If in 
eq. (2), page 639, we substitute the value of h from eq. (3), we have 

C constant 

C = constant X Q s , or the cost per unit capacity =q= - ~q \— 1 that 


* Eng. News , 1895, xxiv. p. 419. 






































652 DISTRIBUTING AND EQUALIZING RESERVOIRS. 

is, the cost of reservoirs per million gallons will vary inversely approxi¬ 
mately as Q s . Thus if a reservoir with a capacity of ioo million gallons 



Longitudinal Section Section of South W&J 1 

Fig. 204.—Montmartre Reservoir, Paris. 


costs $3.00 per thousand gallons capacity, one of 10 millions, similarly 
constructed, will cost about 3 X 10* = about $4.75 per thousand gal¬ 
lons; one of 1 million capacity will cost $7.50, etc. 

The actual cost of several reservoirs is as follows: 


Place. 

Capacity in 
Gallons. 

Cost per 
1000 Gals. 
Capacity. 

Remarks. 

Earthen reservoirs: 

Pittsburg, Highland Park. 

Trenton, N. J. 

Minneapolis, Minn., two, each. 

Cincinnati, O., subsiding reservoirs 

125,000,000 

104,000,000 

46,000,000 

50,000,000 

$ 3-35 

3-37 

4.80 

3-50 

Estimated. 

Covered masonry reservoirs : 

Albany, Ga.. 

280,000 

6.30 

Wooden cover. 

Coshocton, O. 

320,000 

13-47 

Brick dome. 

Franklin, N. H. 

Wellesley, Mass. 

504,300 

18.00 

Brick arches. 

600,000 

17-35 

Concrete cover. 

Rockford, Ill. 

1,000,000 

20.00 

Monier construction. 

Brookline, Mass. 

1,200,000 

22.00 

Brick arches. 

Montmartre, Paris. 

3,000,000 

74.00 

Elevated reservoir. 


























































































































































STAND-PIPES. 653 

Mr. Coffin estimates the cost of circular reservoirs with concrete 
covers as follows:* 


Capacity. 

Gallons. 

Diameter. 

Feet. 

Depth. 

Feet. 

Cost per 1000 
Gals. Capacity. 

500,000 

75 

16 

15.60 

1,000,000 

98 

18 

12.85 

1,500,000 

II 5.5 

19 

II.70 

2,000,000 

125 

22 

II .00 

3,000,000 

144 

25 

10.07 

4,000,000 

166 

25 

9-47 

5,000,000 

186 

25 

9.12 


His estimates for square reservoirs are about 4 per cent higher than 
the above figures. 

STAND-PIPES AND ELEVATED TANKS. 

714. Where a reservoir requires to be artificially elevated it is 
usually built as a stand-pipe—a tall slim tank resting on the ground 
—or as an elevated tank of steel or wood, supported by a tower of steel, 
wood, or masonry. Such an elevated reservoir may or may not be 
enclosed in a covering of masonry or wood, according to the necessi¬ 
ties of the case and the notions of the designer. 

Reservoirs of this type are relatively so expensive that a minimum 
amount of storage capacity is usually provided. As shown in Art.. 
698, they may be used in small towns to enable the pumps to be more 
economically operated, or in larger towns to provide for fire consump¬ 
tion for an hour or so, or in large cities to act merely as equalizers for 
the pumps. The capacities of stand-pipes and tanks range ordinarily 
from 50,000 gallons up to a maximum of about 1,500,000 gallons. 

715. Location.— For storage purposes only, the location would be 
the same as that for any other reservoir, as discussed in Art. 699. To 
reduce the cost it is, however, desirable to place the tank on the 
highest ground available if it be within a reasonable distance. Too 
great distances will be undesirable on account of the cost of mains and 
the loss of head caused by a long line of pipe. If the stand-pipe acts 
simply as a pressure-regulator, it should be located near the pumping- 
station, or at least at some point on the force main before any con¬ 
siderable number of branches occur. 

Stand-pipes. 

716. General Dimensions. —The useful capacity of a stand-pipe is 
only that part of the volume which is at a sufficient elevation to give 


* Jour. New Eng. IV. W. Assn., 1900, xiv. p. 283. 

















654 DISTRIBUTING AND EQUALIZING RESERVOIRS. 


the required pressure. All water below this level acts merely as a 
•support for the portion above. There should therefore first be deter¬ 
mined the lowest useful level of the water, and the pipe should then be 
made of the desired capacity above this plane. The ratio of height to 
diameter should be chosen with respect to the following considerations: 
Cost of pipe and foundation, variation in water-level, cost of pumping, 


and practicable thickness of plates. 

if Q — useful capacity in gallons, H = height of pipe in feet up to 
the lowest useful level, x = additional height necessary to give the 
desired capacity Q, and d = diameter of pipe, then Q — 5.9 xd 2 and 


x d 2 — —, = a constant, = K. The weight and cost of the pipe-shell 
5,9 

are nearly proportional to (H- f- xf and to d 2 , or, Cost = K'd 2 (Hx ) 2 ; 

K (H 4 - x ) 2 

but d 2 — —, whence, Cost = K'K- -. Differentiating, etc., 

;r x 

we find that for a minimum cost, x — H. That is, the total height 


.should be 2 H, and d — 



This result will of course be modi¬ 


fied by the other considerations mentioned above, but the relation 
brought out will aid in selecting the best dimensions. If H is large, 
this rule would be likely to give such a height as to make the variations 
in pressure too great and also give too heavy plates at the bottom, 
plates thicker than i-| inches being undesirable. A high tank will also 
increase the cost of pumping. On the other hand a large diameter will 
increase the cost of foundation. It is on the whole desirable to use 
rather large diameters. With ordinary values of capacity, and with H 
equal to 50 to 100 feet, the best value of x will probably be from f to 
x H. The best proportions can readily be determined by trial estimates 
of cost of pipe and additional cost of pumping per foot in height, having 
regard to the limiting conditions mentioned above. 

If the entire volume can be counted on as useful, then H = o, and 
the best proportions will depend very largely upon cost of foundation 
and cost of pumping. Neglecting the last item, and assuming as before 
that the cost of shell varies as x 2 d 2 and that the cost of foundation and 
bottom plate is proportional to the area, or to d 2 , it will be found that 
the economical height is the same for all capacities, and is in the neigh¬ 
borhood of 25 to 30 feet. The cost of pumping additional height will 
tend to reduce this slightly, while the cost of the upper plates, whose 
thickness must be much greater than required for water-pressure, will 
tend to increase it, so that for very large pipes, 40 feet will be more 
nearly the economical height. 






STAND-PIPES. 


655 


If a stand-pipe is used only as a relief to the pumps, its diameter 
may be made from 3 to 6 feet. A diameter of twice that of the force- 
main would reduce the rate of variation of pressure on the pumps to 
one-fourth that in the mains, which would be sufficient in most cases. 

717. Forces and Stresses.—The forces to be considered in the design 
of a stand-pipe are the water-pressure, the wind-pressure, the weight 
of the pipe, and the action of ice. In what follows let h — distance in 
feet of any point below the top, d — diameter of pipe in feet, r =. 
radius in feet, and t — thickness of shell in inches at any given point. 

The water-pressure causes a stress per vertical lineal inch of pipe 
equal to 

_ 62.5 hd 

6 = ——- = 2.0 hd. .(1) 


2 X 12 


The stress per square inch is 


2. 6 hd 


s — 


(2) 


i he wind-pressure is usually taken at 40 to 50 pounds per square 
foot on one-half the vertical projection of the tank. At the higher 
figure the bending moment in foot-pounds at any distance h below the 
top, caused by the wind, is 


dh h . 

M — 50 x — X — = 12.5 d/d. 


(3) 


This moment causes a maximum stress in the shell of the pipe (the 
extreme fibre) equal to 

My 


s = 


/ 


In this cas ey = r, and I = Jtt (r* — r 2 4 ) = approximately n — r 3 , 

X 2 


(/ in inches,) whence, in pounds per square inch, 

1 Air h 2 

_ * — 

144 ntr 3 


s = 




( 4 ) 


I 2 


and the stress per lineal inch along a circumferential line will be equal 

to 

Jd 


S ' = 1.33 


d 


(5) 


If W — weight of pipe in pounds, the stress per lineal inch due to 
its weight will be 


1 W 


W 









\ 

656 DISTRIBUTING AND EQUALIZING RESERVOIRS. 


and per square inch will be 


i- 


// 


= .026 


W 

dt 


\ • 



Assuming the average thickness above the point in question to be — 

2 

and adding 15 per cent for laps, etc., the weight W will be approxi¬ 
mately equal to 75 dth, and hence s" — 1.9/1, which value will never 
exceed a few hundred pounds. 

Besides the overturning effect of the wind there is to be considered 
the collapsing effect on the empty pipe, especially near the top where the 
plates are thin. This cannot readily be computed, but must be provided 
for by an ample margin of strength at the top of the stand-pipe. 

The effect of ice action is a very serious matter in unprotected stand¬ 
pipes, but is very difficult to calculate or provide for. It may occur in 
various ways. During severe weather a heavy cylinder of ice will form 
next to the shell. A warm spell may cause this to melt somewhat 
around the outside, and then the water in the annular space thus formed 
may again freeze, causing a heavy bursting pressure. Or the water 
may be drawn down a considerable distance after heavy ice is formed 
so that a thaw will allow the mass to drop, thus causing heavy water- 
hammer; or, after the water is drawn down, the pipe may be so 
rapidly refilled as to blow out the ice cover, causing sudden shocks and 
stresses. The importance of this matter is attested by the many acci¬ 
dents traceable to the action of ice.* 

The stresses caused by ice action can only be provided for by the 
use of a good quality of soft steel which will allow of deformation 
without injury, and by the use of a large factor of safety. It may well 
be questioned, in view of the uncertainties of the case, if all metal tanks 
built in cold climates should not be encased in masonry or wood. The 
construction of exposed metal tanks in cold climates would scarcely 
be considered possible in the more conservative European practice. 

718. Material Employed.—The material used for stand-pipes should 
be soft, open-hearth steel, of a tensile strength of about 54,000 to 
62,000 pounds per square inch. The best practice now calls for a 
grade corresponding to flange steel, with phosphorus limit of about 
..06 per cent, an elongation of 22 to 25 per cent, reduction of area of 
50 per cent, and flat bending tests, both cold and after heating and 
quenching. Many stand-pipes were formerly constructed of cheap tank- 
steel, which is doubtless one of the principal causes of the many failures. 


* See reference 14, p. 680. 





S TA ND-PIPES. 657 

% 

Rivets, being hand-driven, are preferably made of wrought iron. Plates 
thicker than f inch should be drilled. 

719. Thickness of Plates.—The safe tensile stress on net section, 
where but little ice is likely to form, maybe taken at about 15,000 
pounds per square inch. Where thick ice is to be expected the work¬ 
ing stress should be reduced to 12,000 or even 10,000 pounds, to 
provide for the unknown ice stresses. The vertical joints will usually 
be so designed as to have an efficiency of 60 to 70 per cent. If 
a — safe stress on net section and e = efficiency, then by eq. (2), page 
655, the required thickness to resist the water-pressure will be 


t — 


2.6 Ad 


ae 



or, if a = 12,000 and e = f, then, approximately, 




2.6/id 

8000 


= .000325 hd. / 



The thickness near the top should not be less than £ inch, or for very 
large pipes, T 5 ^ inch. Plates thicker than 1 inch or i£ inches should be 
avoided. 

The stresses due to wind and weight need not be considered here, 
as they act at right angles to the stresses due to water-pressure and are 
also much less in amount. 

720. Riveting.—The plates forming a stand-pipe are usually of such 
a width as to build 5 feet of pipe, and are from 8 to 10 feet long. Each 
course is preferably made cylindrical, and alternately an “inside ” and 
an “outside ” course. 

The riveting of the vertical seams is the most important part of the 
construction, as this determines the 
strength and economy of the stand-pipe. 

Lap-joints are most commonly used, but 
for thicknesses exceeding J inch, double¬ 
butt strap-joints are much preferable and 
are stronger. The butt-joint is arranged 
as shown in Fig. 205, thus avoiding the 
forging at corners which is necessary with 
lap-joints. 

The maximum economy of riveting 
would be secured by selecting a diameter of rivet such that its shearing 
strength would equal its crushing strength, but in practice the diameter 



r—j 

1 


000000 

'oojoo 

000000 [ 

1 


0 0 



o * o 
do 

o 1 o 










































658 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


selected is usually somewhat less than this, in order to avoid too great 
a pitch and too large a rivet. For lap-joints the diameter is made 
equal to about twice the plate thickness, but not less than -§■ inch nor 
more than i-J or ij inches. For double-butt joints the diameter need 
not be made so great. With the selected diameter, the pitch is deter¬ 
mined by making the tensile strength on net section equal to the 
shearing value of the rivets, using a safe shearing strength of about 
three-fifths of that used for the tensile strength. The efficiency is then 
the ratio of safe stress on net section to safe stress on gross section. 

Joints are single-, double-, or triple-riveted, depending upon the 
thickness of the plates and the economy desired. The efficiency of a 
joint increases with the number of rows of rivets used, but for any par¬ 
ticular style of riveting the efficiency decreases somewhat as the thick¬ 
ness of the plates increases, on account of the limitations to the size of 
rivets. It is therefore of greater relative importance to use multiple 
riveting on thick plates than on thin ones. In stand-pipe construction 
it is usual to employ single riveting for the upper sections where the 
plates are not fully stressed; then double riveting up to a thickness of 
■§■ or i inch, and triple riveting for I inch and above. With a high 
cost of material it would be economical to employ triple riveting for 
thinner plates. 

Table No. 95, from Johnson’s “ Framed Structures,” gives suitable 

TABLE NO. 95 . 

PROPORTIONS FOR RIVETED JOINTS FOR STAND-PIPES. 


Kind of Joint on Vertical Seams. 


Single-riveted lap 


4 4 4 4 4 4 

Double- “ “ . 

<4 4 4 44 

It 41 

4 4 4 4 44 

“ “ butt 

44 44 44 

44 4 4 4 4 

44 44 44 

ti 44 44 

it 44 4 4 

44 44 44 

44 44 44 

4 4 4 4 






E v 





(A 


O tj 


Vh 

O 

C /3 

C /5 

V-J 

0 

u 

0/ • 

Is . 

VM <L> 

C/J 

<u 

C G 
<u 'uig 

S-. —- 

° c>« 

0 

0 c " 

hickne 

Plate. 

*-* 

QJ U 

e.t 

.205 

ott 
c c 
tj <0 v 

= £-5 

CT 3 «-* ♦-* 

«-» OJ 

-Q cu 

5 u bi 
fS.-’O 

.sow 

*-> — rt X 
£ «£ 0 

0 > 

H 

Q 

cu 

Q 

Q 

a 


Inch. 

Inches. 

Inches. 

Inches. 

Inches 



4 

5 

¥ 

5 

¥ 

I| 

If 


I 



5 

TS 


il 


\ 50 


1 8 



5 

16 

e 

¥ 

2f 

2 f 

ik 

> 


8 

¥ 

8 

¥ 

2f 

2k 

14 


- 60 

7 

T<> 

f 

2f 

2 i 

if 


1 

¥ 

7 

¥ 

2| 

2» 

ik 


1 

9 

T¥ 

7 

¥ 

2 I 

2# 

if 

] 


5 

8 

7 

¥ 

2 f 

2| 

if 



1 

T 6 

I 

2 f 

2 f 

if 



3 

T 

1 3 

1 6 

I 

I 

3 

3 

2k 

2k 

if 

if 


^70 

7 

8 

if 

3 

2 k 

2 



1 5 
T 6 

I ¥ 

3 

2 h 

2 



I 

I 4 

3 f 

2f 

2 f 



I 

4 

4 

3 

2 f 


75 


Triple- 










































STAND-PIPES. 659 

proportions for riveted joints, together with their efficiencies, as com¬ 
piled from the Watertown Arsenal reports. 

Horizontal joints are made single-riveted lap-joints, with rivet spac¬ 
ing of about three diameters. The wind-stresses will not require con¬ 
sideration unless the pipe is extraordinarily tall and slim. They can in 
any case easily be considered by the use of eq. (4). All seams should 
be thoroughly calked with a round-nosed calking-tool, and any leaky 
seams which may exist when the pipe is filled should be recalked. 

721. Bottom Details.— The bottom is made of plates riveted up with 
circular and radial joints, the former being made lap-joints and the 
latter butt-joints. The thickness need be only enough to permit of 
good calking and to be durable,—about % inch. This bottom plate is 
preferably connected to the side plates by means of a heavy angle on 
the outside, or one on both outside and inside the tank. The riveting 
of the side plates to the bottom angle is referred to in the next article. 

In erection, the bottom is riveted up and attached to the lower course 
of the side plates while supported a short distance above the foundation. 
The foundation is then prepared and the bottom carefully lowered 
thereon. To furnish an even bearing and to level up the foundation, 
a dry mixture of cement and sand is often used, in order to avoid any 
trouble from setting before the work is in place. Grout has also been 
used by forcing it through holes in the bottom while the latter is 
supported about an inch above the foundation. The holes are after¬ 
wards plugged up. 

722. Foundation and Anchorage. —The foundation should be made 
monolithic and sufficiently broad to give such low pressures on the soil 
that there will be practically no settlement. Failures have occurred 
due to poor work in this respect. Wind-pressures should be carefully 
considered. Concrete is a very suitable material for foundation purposes. 

Stand-pipes must be anchored to the foundation to prevent being 
overturned by the wind. Eq. (5), page 655, gives the tensile stress 
per lineal inch, circumferentially, at any point in the pipe due to wind. 

h 2 

It k S' — 1.33-^. The effect of the weight of the pipe in reducing 

this need not be considered. The stress on any anchor-bolt will then 
be S'p , where p — distance in inches between bolts. If numerous 
bolts are used, their size will not be great, and they may be put through 
the exterior bottom angle and the latter double-riveted to the pipe. If 
arranged in this way, they should be numerous enough so that the stress 
in one bolt is not greater than can be transmitted to the lower plates 
by four or five rivets, which will limit the size of bolts to about 1} times 


66 o 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 



5 

- 


0 


O 

0 


0 

0 


0 

0 


0 

0 


0 

0 


0 

0 


0 

0 


0 

0 


0 

0 


0 

0 


0 

0 


0 

0 


0 



the diameter of the lower rivets. By spacing the bolts sufficiently close 

this arrangement may be followed in almost 
any case. If this method gives a large number 
of bolts, it will be simpler to use fewer and 
larger bolts, in which case they should be 
fastened to the stand-pipe by long vertical 
pieces of angles, and the bolts placed close to 
the pipe as shown in Fig. 206. The number 
of bolts should not be less than six in any 
case. Anchor-bolts should extend well into 
Fig. 206. the masonry and be fastened to anchor-plates 

embedded therein. 

The method here given for determining the stress in anchor-bolts 
is not equivalent to the usual method of equating moments about the 
edge of the pipe, but gives larger values than that method. It is the 
same as would be used at any other horizontal joint of the pipe, or at 
any section of a beam, and it assumes that a tension will exist on the 
windward side before the resultant pressure reaches the outer edge of 
the joint—in fact as soon as it passes the edge of the “ middle third,’ ’ 
as is the usual assumption in all masonry designs. 

With very high pipes, and on soft soils requiring broad foundations, 
it may be desirable to distribute the pressure by the use of large 
brackets of a triangular shape, riveted to the pipe, at the outer ends of 
which the anchor-bolts may be placed.* These bolts may be figured 
in the same way as explained above. For very slender tanks, stays or 
guys of wire are sometimes used. These should be very taut so as 
to prevent injurious deflections. 

723. Pipes and Valves. —Usually a single pipe serves both as inlet 
and outlet. This passes through an arched opening in the foundation, 
turns upwards and enters the stand-pipe 
at the bottom, and extends into it a 
foot or two. A lead joint is usually 
made in a bell casting riveted to the 
bottom of the pipe as shown in Fig. 

207. Another arrangement is shown 
in Fig. 208, which illustrates the details 
of the bottom of the West Arling¬ 
ton stand-pipe, Baltimore, Md., Mr. 

Nicholas J. Hill, chief engineer. The 
inlet- and overflow-pipes are of steel. 



Fig. 207.—Inlet-pipe for Stand¬ 
pipe. 


* 


See Johnson’s Framed Structures, p. 430. 
















































STAND-PIPES. 


66 1 

They are riveted to steel flanged collars at the entrance to the pipe, 
and to similar collars bolted to the flanges on the cast-iron elbows 
which rest on the concrete. 




Fig. 208.—Bottom Details, West Arlington Stand-pipe, Baltimore, 

(From Engineering Record, Vol. xl.) 


A drain-pipe through which the tank may be drained or flushed 
should be provided. Such is also shown in Fig. 208. Overflow-pipes 
are not usually provided for open stand-pipes. If used, they should be 
placed on the outside, the water reaching them from over a broad weir 
or through an orifice in the side of the tank. Valves for inlet- and 
drain-pipes should be placed outside the foundations. 

Where the fire pressure must be furnished for the most part by 
direct pressure, some convenient method of shutting off the pipe must 
be employed, and right here is where the ordinary system is apt to be 
weak and out of repair. Several devices are in use for closing a valve 
by electrical means. A simple form of such device consists of an 
ordinary gate-valve, operated through suitable gearing by means of a 
weight attached to a drum which can be released electrically. The 































































































































662 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


valve is opened by hand.* Another general form consists of a check- 
valve arranged to be operated by an hydraulic piston, the water for 
which is supplied from the force-main and controlled by a small valve 
operated electrically. + 

Another simple form is where an ordinary hydraulic gate-valve is 
arranged to be operated by an electrical device. Other devices are 
employed which act automatically when the pressure or velocity of the 
water is increased. These are apt to cause heavy water-hammer, 
unless specially guarded against by the use of a balanced valve or by 
relief-valves. J 

Whatever the device used, unless the valve opens as well as closes 
automatically, a by-pass with check-valve should be provided to 
enable water to flow from the stand-pipe in case the pressure in the 
mains falls below that in the stand-pipe. 

High-water electric alarms are advisable if the pipe be at some dis¬ 
tance from the pumping-station. The pressure indicated at the station 
is not a certain guide if branch mains are led off at intermediate points. 
For encased pipes or tanks a simple float, arranged to close an electric 
circuit, may be used. For exposed pipes, ice is likely to interfere, and 
in this case a pressure-gauge placed in a vault and connected to the 
stand-pipe can be arranged to give an alarm at any desired pressure. 
For encased stand-pipes the balanced float-valve described on page 
452 may be used to advantage to shut off the supply. 

724. Other Details. — Top Angle .—The top should be stiffened 
against collapse by a heavy angle-iron, not less than 3X5 inches, and 
two such angles should be used for large pipes. The effect of the Wind 
on an empty pipe is not only to cause a pressure on the outside, but 
to create a partial vacuum on the inside near the top. Several 
failures have occurred from lack of strength at this point. 

Roof .—It is not customary to roof stand-pipes, and for a tall slim 
pipe a roof would be of little use and no improvement to its appearance. 
With large, low pipes a conical roof of curved profile may well be 
adopted. It affouds considerable protection and improves the appear¬ 
ance of the structure. It is usually made of sheet iron or copper, sup¬ 
ported on light angle-iron ribs or framework. 

Ladder .—A ladder should be built on the outside of the pipe, but 
none on the inside; and in general there should be no obstructions on 
the inside where ice is likely to form to any extent. 

* Eng. News, 1889, xxu. p. 291. 

f Eng. Record , 1894, XXIX. p. 339; 1900, XVII. p. 177. 

\ See description of automatic valves in Eng. Record, 1894, XXIX. p. 339; Eng. 
News , xxxi. pp. 12, 284. 









STAND-PIPES . 


663 


Manhole .—A manhole is sometimes placed in the lower course of 
plates. If this is done, care should be taken to properly reinforce the 
cut plate. In Fig. 209 this is accomplished by an angle and a cast- 
steel frame. 



Fig. 209.—Manhole, West Arlington Stand-pipe. 


Ornamentation .—Besides the use of a roof as noted above, the 
monotony of a low stand-pipe may sometimes be broken up by a wind¬ 
ing staircase. For a very tall pipe little can be done, perhaps, to im¬ 
prove the appearance. The chief cause of the ugly appearance of such 
pipes is the lack of any apparent base. A massive masonry pedestal 
of a height proportioned to that of the tank, used in connection with 
a suitable cornice, would improve the appearance considerably.* 

Painting. —Stand-pipes should be well painted inside and out. 
For the interior, asphalt is probably the best material to use. After 
painting the interior, the pipe should be filled to detect leaks before 
the outside is coated. 

725. Encased Stand-pipes. —A stand-pipe is often surrounded with 
a masonry shell in order to furnish protection from cold, or to im¬ 
prove the appearance of the structure, or, in the case of slender pipes 
such as are used for pressure-regulators, to protect them from wind- 
pressure. The masonry shell may be of stone or brick, and is usu¬ 
ally built enough larger than the pipe to permit of a stairway in the 
space between. For small towers the walls can be calculated as if the 
structure were a monolith, according to the principles applied to other 
masonry structures, the wind-pressure and the weight of masonry being 


* See illustration in Johnson’s Framed Structures, p. 433. 






























664 DISTRIBUTING AND EQUALIZING RESERVOIRS. 

the forces considered. The resulting walls will vary considerably in 
thickness from top to bottom. They are usually made from 2\ to 4 
feet thick at the bottom and i|- to 2 feet at the top. With pipes of 
large diameters (25 to 40 feet) the results of analysis under the 
assumption of a monolithic structure would give walls too thin to be 



Fig. 210.—Compton Hill Water-tower, St. Louis. 

(From Engineering News , vol. xxxix.) 

stable locally, and it cannot well be assumed that such walls act as 
monoliths. Under such conditions it may be best to provide against 
wind-pressure by the tank anchorage, and then brace the walls against 
the tank, as was done at St. Charles, Mo. In this case, with a tank 
25 X 70 feet, the walls were supported at six points by circular lattice 
girders 2 feet deep riveted to the tank. At the same time these 
girders served to strengthen the tank against buckling. The walls were 
from 9 to 13 inches thick.* 


* Jour. Assn. Eng. Soc ., 1895, xiv. p. 533. 

















































































































































ELEVATED TANKS. 


66 $ 


Encased pipes must be provided with overflows, which may be built 
either inside or outside the main pipe. For this type of structure, 
roofs are quite necessary, and should be carefully proportioned with 
respect to appearance. The masonry offers considerable opportunity 
for architectural treatment, and this feature should be referred to a 
competent architect. 

A small encased stand-pipe built near a pumping-station is illus¬ 
trated in Fig. 210. The stand-pipe is provided with a 2-foot overflow- 
pipe which is connected at two points with the main pipe. Either 
connection may be used, according to the pressure required. In the 
design of this structure the architectural features were of considerable 
importance, the tower being located in a prominent place. The base 
of the tower is of blue Bedford stone, the sub-tower of white limestone, 
and the main shaft of buff brick, trimmed with granite. The roof is of 
white tile. The tower is lighted by electricity. 

Elevated Tanks. 

726. Economy of Elevated Tanks. —If the lower portion of the water 
i»n a stand-pipe is at too low an elevation for useful pressure, its only 
office is to furnish support to the useful part above. Where this useless 
zone is of any considerable depth the support can be more cheaply 
furnished by a steel trestle. Assuming the safe compressive stress in 
the columns of such a trestle to be 10,000 pounds per square inch, the 
total cross-section of the columns necessary to support a tank above 
any given plane will be about one-half that of a stand-pipe at the same 
elevation. The thickness of a stand-pipe would also increase rapidly 
from this point down, while the column sections would increase but 
slightly. The economy of the trestle form is therefore very evident 
where the distance to the useful elevation is considerable. The cost 
of piping, trestle-bracing, etc., would add to the expense of the tank, 
but the foundation for a tank is less expensive than that for a stand-pipe. 
Besides being cheaper, a tank is much less objectionable in appearance 
than a stand-pipe, and experience indicates that trouble from ice is less 
likely to occur. 

727. Form and Proportions. —For roofed tanks a height equal to the 
diameter would not be far from the most economical proportions, but 
a height somewhat greater than this will usually look better. 

Formerly the bottoms of tanks were made horizontal and supported 
on a system of beams, but later designs use a conical or a spherical 
bottom supported at the periphery only, which is a better and much 


666 DISTRIBUTING AND EQUALIZING RESERVOIRS. 

cheaper arrangement. The spherical form is the best, and involves no 
special difficulty in construction. A hemispherical bottom gives lower 
stresses to be provided for than the segmental form, but rather more 
complex details at the supports, so that the latter may be preferred, 
especially where the tank rests upon masonry walls. The hemispheri¬ 
cal form has, however, been adopted as the standard by at least one 
large construction firm. 

728. Stresses in Tank, —The thickness of side plates is the same as 
for stand-pipes, and the details are similar. If the bottom is spherical, 
the tension per lineal inch will be one-half that in a cylinder of the 
same radius and with the same internal pressure, or by eq. (1), page 
655, will equal 

5 = 2 .6hr, .(10) 

in which r — radius of bottom, and h — head of water in feet. For a 

d. . 

hemispherical bottom, r — —, and hence the thickness of plates would 

be equal to one-half that of the lowest side course (assuming same 
efficiency of joint), but should not be less than T 5 6 or f inch. 

To analyze the stresses in a conical bottom it will be convenient 
to consider the tensile stresses along an element of the cone, and those 
at right angles thereto, separately. 

Fig. 211 shows the portion of a conical bottom below any section 



Im. W is the total weight of water directly above the section, 
together with the small weight of water and tank below, and 5 is the 
tensile stress per lineal inch. Assuming no bending stresses to exist, 
we have 

5 sin 6 X 12 X 2 7rp = W, 


whence 









ELEVATED TANKS. 


667 


in which p is in feet. If h — average head of water on this portion of 
the bottom, we have (neglecting the weight of tank) W = 62. $hnp 2 y 
whence 


5 = 2 


6 


ph 
sin 6 



At the edge of the tank 5 is a maximum and is equal to 2.6 -——. 

sin 6 

For 6 = 30° this would be the same as the stress in the lowest side 
plate (eq. (1), page 655). 



The tensile stress in a circumferential direction will now be deter¬ 
mined. Fig. 212 shows one-half of a horizontal slice of the bottom, 
one foot in vertical dimension. S x and 5 2 are the stresses per lineal 
unit, acting in the directions indicated, and P is the stress to be deter¬ 
mined. The length AB = and is the same as the length over 

which P acts. The average head is h, the average radius is p, and 



















668 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


the water-pressure per lineal unit is w. Equating horizontal compo¬ 
nents, we have, by a summation similar to that performed in getting 
the bursting stress in a pipe, 


P = S x cos 0 p x — S 2 cos 0p 2 -f- w sin 6p. . 

Equating vertical components, we have 

S l sin Orp l — 5 2 sin 0 np 2 = w cos 0 np\ 
whence we may write 

cos 2 0 


Furthermore, w — 


cos 0p x — S 2 cos 0p 2 — wp -^7 
62.5 h 


sin 0 


• • 


an O' 


Substituting in eq. (13) from eqs. (14) and (15), we have 

'cos 2 0 \ 

+ I • • 


/cos 2 0 \ 

P — wp —-- 4 - sin 0 ) — 62. 5 ph I . „ 

Vsin 0 ^ / Dl \sm 2 0 


■ (13) 


• 04 ) 


• (IS) 


(i6> 


The stress per lineal foot will be P sin 0 y or, expressed in pounds per 
lineal inch, it is 


^, P sin 0 ph 

S’ = -— = 5.2 -- 


12 


sin 0 


07 } 


This is just twice the stress given by eq. (12), and is greater than the 
stress in the lower side plates in the ratio of 1 : sin 0. To avoid too 
thick bottom plates, therefore, 0 should not be made small. 

729. Connection between Side and Bottom Plates. —With a conical or 
segmental bottom the inclined pull per, inch at the line of connection 
with the side plates will be given by eq. (11). It is 


5 


W 


.0132 


r sin 0* 


where W = total weight of water and of bottom, r = radius of tank, 
and 0 — angle of inclination with the horizontal of cone element, or of 
tangent to circular segment at outer edge. The bottom and sides are 
connected by means of a circular angle or shape iron, which resists the 
horizontal component of the force S, by compression as a ring. The 
compressive stress in this ring will be 

P' ~ 12S cos Or = . 159 IE cot 0 y .... (18) 

or approximately 

P' = 31 -2/:r 2 cot ( 9 , . ..(19) 

Where k = average depth of water. This is a very considerable stress. 











ELE VA TED TA NKS. 


669 



and must be provided for by a sufficient amount of metal, but the metal 
of the side plates and of the bottom plates can be counted on for 

5 or 6 inches from the angle. The hemispherical bottom causes 
no stress of this kind and is in this way 
preferable. 

Fig. 213 illustrates three simple ar¬ 
rangements of this detail. The bent 
bottom plate should in the first two cases 
be supported close to the line of the 
bend. For other details see Figs. 214 and 217. 

730. The Tower. —The tower consists of a steel trestle of four to 
eight legs. The material for this may be medium steel, and compara¬ 
tively high working stresses may be used in its design, since the 
stresses are all dead- and wind-load stresses. Four legs are the 
smallest practicable number, but for tanks of large diameters the use 
of only four legs brings very heavy local stresses on the tank at the 
points of connection. Six or eight is a better number and presents a 
better appearance, but is more expensive. A design in which four 
posts are used and branched near the top was employed by Johnson 

6 Flad at Laredo, Texas, and again by Mr. Flad at Murphysboro, Ill. 
The latter design is illustrated in Figs. 216 and 217. This arrange¬ 
ment gives twelve points of support without the use of an expensive 
tower. The tank is sheathed with wood to prevent the formation of 
ice. 


The columns of the tower may be of channels, Z bars, or any con- , 
venient form of section. They are supported at intervals of 20 to 30 
feet'by lateral bracing, which also forms the wind-bracing. This, 
bracing usually consists of horizontal struts and diagonal tie-rods. 
For eight or more legs radial struts should also be used to give rigidity 
to the tower. In high towers the columns should preferably have a 
broken outline for the sake of appearance, as in Fig. 215, which illus¬ 
trates the large tank at the Iowa Agricultural College at Ames, Iowa,, 
Prof. A. Marston, engineer. This was the first tank in which this, 
feature was carried out. The details of this tank are shown im 
Fig. 214. 

731. Stresses in Tower .—The stresses due to the vertical load are 
readily calculated, and for the four-post tower those due to wind also. 

In the six- or eight-post tower the wind-stresses are not so readily 
determined. The following method was first suggested by Prof. 
Marston.* 


* Eng. News, 1898, xxxix. p. 371 
















670 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


2 

1 


I 



L, 6 k 6 ’ 4 ‘ 


s-4xJxb'T 


Loft Bars, 
,/'J'~.d 
'i x i» 


Section 

A-A. 


: n*” 

-AxSx^Stiff.E\ 

A* ¥&r 


•"Mdo 




Section B'B. 





L, 6 x 6 xfi 


***** 




Vertical Section 
E-F. 


Balcony Laid with 
1%'Oah Floor, Fastened 
to Nailing Strips, . _ 
Boh*dtv6’L s . b ‘ 


Stiff. L 



Sectional Plan C“ 0 . 



Bale. 
Steel Irani 


* Sheet Metal mfh 
Strap Iron Brackets 
every S‘ft. 



Ei'°Anchor 
Bolts 



PfnHokfor 
Lateral Rod 
Conn. 

? Conn. fi... 1?*° 
; 


?x 5 ‘x£ ' 


^Xjsteel 


Section ..AnB 


Elevation. 

cm* 

Qptnincj-r 



.BentPP 

SiJxf 

tk‘°Stone 

Bolt 


B 

Sectional Plan. 



Section C-D. 


O' )' 

U<uiiL 


4 Splice 
4 &xf 



Pine. Hole for 
Lateral Rod ^ 
Connections 


■\~Z 

s Connection PI. 

dr 


o O 

0000 


i\VA\> 1 


Lateral Strut 
4 IS, Laced 


A 



Section A-B. 


Fig. 214.—Details of Elevated Tank at Ames, Iowa. 

(From Engineering News, vol. xxxix.) 


















































































































































elevated tanks. 


6 75 


The amount of wind-pressure on the tank may be assumed the 
same as given for stand-pipes. On the tower a pressure of 50 pounds 
per square foot of all exposed areas may be assumed. As regards 
wind-stresses the tower may be considered as a vertical cantilever 



-f 4 '*IO"W.P. 

"LS 

. Circular 6ird « f, 



fe^ 


Elevation. 


Tank details. 
Fig. 216.— Elevated Tank, Murphysboro, III. 

(From Engineering Record , vol. xlii.) 


)eam anchored to the ground. Then if we pass a horizontal section 
it the top of each story, cutting the posts only (between points of 
Lttachment of diagonal bracing), we can get the vertical components 
>f post stresses as in a beam made up of parts. Thus in big. 218, 































































































674 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


representing such a section, let A = section of each post, and r — 
radius of tower. The maximum stress in post a will occur when the 
wind blows at right angles to axis Im. If M is the wind moment 
about the horizontal plane assumed, the fibre-stress in posts a will be , 


4iK"§’l , \ 




Pinhole. - 
I 



f jf iL z ' io *- iU 

f- 3 ' 6 '-U -^ 54 f—!-!— 

i I I J. I I i li 


C lone Cap. 1J Tooth Chiseled 


U PBotts.-Q 

Foot of Main Columns., ^ 
Fig. 217 .—Details of Elevated Tank, Murphysboro, III. 

(From Engineering Record , vol. xlii.) 


Mr 


jr __ where I — moment of inertia of the entire tower about Im, = 


4 Ar 2 , if we neglect the moment of inertia of each column about its 

M 


own axis. Hence /= —r, or the total column stress = 

4 Hr 


P = fA — 


M 


4 r 


(20) 


M 


The stress on columns b — .7—, and on columns c y 


o. 



































































































1 . • 






ELEVATED TANKS. 0/5 

In a six-post tower I — 3 Ar 2 , and the stress in the most remote 

. M 1 jif 

post is —, and on each of the others is- 

2 3 r 

By this method the vertical components acting at the top and 
bottom of each story at each post can be found. Then taking each 
story separately, the stresses in the diagonal rods can be found by 
equating vertical components acting at top 
and bottom of each post, beginning with 
the post a where the stresses on the two 
diagonals attached thereto are equal. The 
actual post stresses are then found by equa¬ 
ting vertical components at either top or 
bottom joint, and finally the stresses in the 
lateral struts are obtained by the use of two 
equations of the components in a horizontal 
plane acting at a joint. 

The wind-stresses should be combined 
with maximum dead-load stresses to get the 
maximum post compression, and with minimum dead-load stresses to 
get the tension on the windward post and the pull on the anchorage. 

732. Connection of Tower and Tank.—With conical or segmental 
bottoms the lower side sheets are usually extended below the bottom 
and finished with two angles as flanges, which rest on the tops of the 
columns, as in Fig. 213. With hemispherical bottoms the extension 
of the lower sheets is unnecessary, as a central connection can readily 
be made to the side and bottom plates as shown in Fig. 214. Ample - 
stiffness should be provided, and sufficient reinforcement to enable the 
column load to be safely distributed into the side plates. With but 
four posts the lower course of side plates should be thickened. Lateral 
stiffness is secured by riveting to the tank, at the level of the post con¬ 
nection, a circular plate or lattice girder supported on brackets, and 
which may at the same time serve as a floor or support for a balcony. 

733. Anchorage.—Each column must be well anchored to the 
foundation, with a strength of anchorage equal to the maximum uplift 
due to wind acting on empty tank. The amount of this uplift is 
computed as explained above. The foundation should be rigid, 
and large and heavy enough to serve as anchorage and to give only 
safe pressures on the ground. There should be practically no settle¬ 
ment, as any unequal settlement will greatly change the stresses in 
the tower. 

734. Inlet-pipe.—The inlet-pipe is usually made to enter the tank 



l 

1 


4 

6 o 

• 

c n 

1 

1 

1 

1 

.6 

<> 


1 

1 

V-s 

1 

- — a 

6 * 

---C 3 — 

VJ 

*>6 


1 

i /77 



Fig. 218. 





6?6 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


at the center of the bottom, and should be provided with an expansion- 
joint. This may consist of a brass-lined stuffing-box and gland or a 
joint similar to that shown in Fig. 165, b, page 557, may be used to 
advantage. In cold climates the pipe must be protected by a frost¬ 
casing, which is usually a simple wooden box with one or more air¬ 
spaces and perhaps a packing of some non-conductive material. If 
the tank is encased, it will be necessary to provide an overflow-pipe. 

735. Masonry Towers.— It is the common practice in Europe to 
support the tank on a masonry structure, and also to enclose it 
with masonry or wood. This form of construction readily lends 
itself to effective architectural treatment and should be more often 
adopted in this country. The bottom details in this case are ar¬ 
ranged as shown in Fig. 213, the tank resting upon the wall. The 
masonry or wood casing above must then be bracketed out. To 
economize in masonry a method of construction devised by Engineer 
Intze has frequently been employed in Germany. This is illus¬ 
trated in Fig. 219, which shows a section of the tower at Kreuz- 

berg, Berlin.* The tank has a capacity of 
about 100,000 gallons. 

736. Wooden Tanks. — Elevated tanks of 
wood are frequently used where low first 
cost is an essential element and the quantity 
to be stored does not exceed 50,000 to 
75,000 gallons. Wooden tanks are cheap, 
and if well built will last fifteen or twenty 
years. The staves should be of good clear 
material and should be dressed to proper 
curvature on the outside. Hoops should 
be relatively thick to resist corrosion, and 
should be thoroughly coated with asphalt 
or other protective coating, before being 
put in place. Lugs and fastenings are a 
source of weakness. They should be care¬ 
fully designed and of ample strength. The 
support of the floors must also be well 
looked after. The chief source of trouble 
with wooden tanks is in the weakening of 
the hoops by rusting from the inside. Galvanizing is now bein g- tried 
as a preventive, and may prove more successful than coatings formerly 





Fig. 219.—Intze Tower 
at Kreuzberg, Berlin. 


* Zeit. d. Ver. deutsch. Ing 1886, p. 28. 








































STORAGE OF WATER UNDER PRESSURE. 


6 77 


used. Several failures of wooden tanks have occurred by the sudden 
bursting of the hoops, and it is questionable policy to construct such 
tanks where their failure is likely to endanger life, as it is quite certain 
that they will not be regularly inspected as they should be. 

737. Storage of Water under Pressure. —In direct-pressure systems, 
some elasticity is to be desired to lessen the shock on the pumps and 
mains due to sudden variations in the draught. The small stand-pipe 
used for regulating the pressure has already been described. Another 
means of furnishing a small amount of elasticity is by means of large 
air-chambers placed on the mains near the pumps. Such have been 
used in a number of cases.* The air can readily be supplied when 
required by means of a small auxiliary chamber placed below the main 
chamber and so connected that air can be admitted to it under no 
pressure; then by closing the inlet and opening the connection to the 
main tank the air may be forced into the latter by the water-pressure 
from the force-main. 

In small works, air-chambers or their equivalent may also be used 
to provide a considerable storage of water and thus avoid the use of 
stand-pipes or elevated tanks. In the design of such storage-tanks 
the larger the proportion of air-space the less will be the variation in 
water-pressure as the tank is emptied. If V = volume of tank, and 
v — maximum volume of water stored, then V — v = minimum volume 
of air. If the pressure, when containing the maximum volume of water, 


be P } then when the tank is just empty the pressure is p = pi^i — 


*) 

V) 


v 1 

Thus if = —, then p — %P y and the variation in pressure is one- 

r 3 

third the maximum. The less the desired variation in pressure the 
greater must be the tank capacity for a given water capacity. The 
air can be maintained in the tank by the same method as previously 
explained. 

A system of pressure-storage having several advantages over that 
just described is the Acme Company’s system, based on patents of 
Wm. E. Wortham and Oscar Darling. In this system the air is stored 
in a separate tank at a higher pressure than is ordinarily kept on the 
water. By reducing-valves in the connecting pipes, the pressure on 
the water may be maintained constant, or may be increased in case of 
fire. Air-compressors must be used here to keep up the air-supply. 
A number of plants of this kind have been installed. (See references 


* See Eng. Record , 1893, xxvil. p. 196; 1893, XXVIII. p. 15c; 1899, XL. p. 55. 





678 DISTRIBUTING AND EQUALIZING RESERVOIRS. 

12, 17, page 681.) The use of a pressure storage system avoids all 
trouble from ice, and for very small quantities is cheaper than an 
elevated tank. A storage-tank can also be located at the pumping- 
station and the pressure easily controlled. For large quantities the 
system would be very expensive. 


LITERATURE. 

EARTHEN RESERVOIRS. 

1. The Brooklyn Water-works Extension. Eng. News, 1891, xxvi. p. 74. 

2. Schuyler. Use of Asphalt for Reservoir Linings. Trans. Am. Soc. 

C..E., 1892, xxvii. p. 629. 

3. Payson Park Reservoir, Cambridge, Mass. Eng. Record, 1895, xxxin. 

p. 25. 

4. Hill. The Water-works of Syracuse, N. Y. Trans. Am. Soc. C. E., 

1895, xxxiv. p. 23. 

5. Stanton. Suggestions for a New Method of Dam Building. Trans. Am. 

Soc. C. E., 1896, xxxv. p. 70. Valuable discussion on the use of 
asphalt. 

6. Le Conte. Asphalt Linings for New and Old Reservoirs. Proc. Am. 

W. W. Assn., 1896, p. 230. 

7. The New Highland Park Reservoir, No. 2, Pittsburg, Pa. Eng. Record, 

1897, xxxvi. p. 54. 

8. New Reservoirs of the Minneapolis Water-works. Eng. Record, 1897, 

xxxvi. p. 312. 

9. Ely. The Queen Lane Division of the Water-works of Philadelphia. 

Describes the relining of a defective reservoir with asphalt. Proc. 
Eng. Club Phila., 1897, xiv. p. 51. See also Eng. Record, 1897, 
xxxv. p. 361; Eng. News, 1896, xxxiv. p. 164. 

10. Special Features of the Reservoirs at Cambridge, Mass., Water-works. 

Eng. News, 1898, xl. p. 324. 

11. The Steubenville Water-works. Eng. Record, 1898, xxxvm. p. 360. 

12. Recent Reservoir Linings. Eng. Record, 1899, xl. p. 77. Describes 

linings of three reservoirs. 

13. The New Water-works of Latrobe, Pa. Details of reservoir, etc. Eng. 

Record, 1900, xli. p. 294. 

14. The Bright wood Reservoir, Washington, D. C. Eng. Record, 1900, 

xli. p. 193. Details of large cast-iron intake-tower. 

15. Whipple and Jackson. The Action of Water on Asphalts. Paper before 

the Brooklyn Engineers’ Club. Eng. News, 1900, xliii. p. 187. 


COVERED RESERVOIRS. 

1. Morris. Covered Service-reservoirs. Proc. Inst. C. E., 1883, lxxiii. 

p. 1. Many reservoirs described and illustrated. 

2. Covered Reservoir, Hudson, Wis., Water-works. Eng. News, 1890, 

xxiii. p. 249. 

3. Covered Reservoirs at Newton, Mass. Eng. Record, 1891, xxiv. p. 418. 


LITER A TUBE. 


679 


4. The Covered Water-works Reservoir at Franklin, N. H. Jour. New 

Eng. W. W. Assn., 1892, vix. p. 82; Eng. News, 1892, xxvn. 
p. 486. 

5. Tomlinson. On Covered Service-reservoirs. Proc. Am. W, W. Assn , 

1893, xiii. p. 43- 

6. Stowell. Covered Reservoir at Rockford. Ill. Jour. Assn. Eng. Soc., 

1894, xiii. p. 52S; Eng. News , 1894, xxxi. p. 162. Monier con¬ 
struction. 

7. Ewart. The Maligakanda Service-reservoir, Columbo. Proc. Inst. 

C. E., 1894, cxvi. p. 284. Repairing cracks in concrete. 

■8. Johnson. Basin and Well-covering of the Waltham Water-works. Jour. 

New Eng. W. W. Assn., 1894, vm. p. 120; Eng. A r ews, 1893, xxx. 

P< 497 - 

9. Forbes. Covered Reservoir at Brookline, Mass. Jour. New Eng. 
W. W. Assn,, 1894, vm. p. 113; Eng. Neivs, 1893, xxx. p. 498. 

10. Dutoit. Precautions in the Construction of Large Masonry Reservoirs. 

Annales des Ponts et Chaussees, June, 1895; Eng. News, 1895, 
xxiv. p. 419. 

11. Covered Reservoir at Wellesley, Mass. Eng. News, 1897, xxxvm. 

p. 223. 

12. Gwinn. Covering a Storage-reservoir at Quincy, Ill. Eng. News, 1898, 

xxxix. p. 373. Wooden cover used. 

13. Fuller. Covered Reservoirs. Jour. Assn. Eng. Soc., 1899, xxm. 

p. 119. 

14. Williams. Lining a Reservoir near Whitby. Proc. Inst. C. E., 1899, 

cxxxvii. p. 357. Asphalt-concrete lining. 

15. Coffin. Design of Covered Reservoirs. Jour. Assn. Eng. Soc., 1899, 

xxm. p. 1. 

16. Allin. Covered Reservoirs at Pasadena, Cal. Eng. A'ews, 1899, xlii. 

p. 101. Contains bibliography on covered reservoirs. 

17. Metcalf. The Groined Arch as a Covering for Reservoirs and Sand 

Filters: its Strength and Volume. Trans. Am. Soc. C. E., 1900, 

XLIII. p. 37. 

18. Gregory. Diagram for Determining the Volume of Semielliptical Groined- 

arch Vaulting. Eng. News, 1900, xliv. p.130. 

19. A Small Concrete and Expanded-metal Reservoir. Eng. Record, 1900, 

xlii. p. 366. 

20. Shields. Covered Reservoirs. Eng. News, 1900, xliii. p. 70. Descrip¬ 

tion of two reservoirs. 


STAND-PIPES. 

1. Kiersted. Stand-pipes. Paper at the Rensselaer Poly. Inst. Eng. 

Record, 1891, xxm. p. 343. 

2. The Des Moines, Iowa, Stand-pipe. Eng. News , 1892, xxvn. p. 346. 

3. Stand-pipe at Roland Park, Baltimore. Eng. Record, 1892, xxvi. 

p. 232. 

4. The High-service Water-tower at Yonkers, New York. Masonry en¬ 

closed. Eng. News, 1892, xxvn. p. 494 * 

5. Coffin, F. C. Stand-pipes and their Design. Jour. New Eng. W. W. 

Assn., 1893, vm. p. 202; Eng. News, 1893, xxix. p. 242. 





68o 


DISTRIBUTING AND EQUALIZING RESERVOIRS. 


6. A High- and Low-service Stand-pipe at Atlantic City, N. J. Eng. News y 

1893, xxx. p. 188. 

7. Coffin, W. C. The Construction of Iron and Steel Water-tanks. Paper 

before Eng. Soc. Western Pa. Eng. Record , 1893, xxvm. p. 139. 

8. The Prospect Park Stand-pipe, Brooklyn. Masonry enclosed. Eng* 

Record , 1893, xxvm. p. 380. 

9. The Norwood, 0 ., Water-tower. Eng. Record, 1894, xxx. p. 253. 

10. Stand-pipe at Chevy Chase, Neb. Eng. Record, 1895, xxxn. p. 298. 

11. Flad. On Encased Pipe with Special Provision for Wind-pressure.. 

Jour. Assn. Eng. Soc., 1895, xiv. p. 533. 

12. The Washburn Park Water-works, Minneapolis. Masonry-encased 

stand-pipe. Eng. Record, 1895, xxxn. p. 259. 

13. Murphy. A Mathematical Investigation of Stand-pipe Failures. Eng. 

News, 1894, xxxii. p. 128. 

14. Stand-pipe Accidents and Failures. The record of stand-pipe failures is 

brought up to April, 1895, in an important series of articles by 
W. D. Pence in Eng. News, 1894, xxxi, and 1895, xxxm. p. 267. 
These are also published in book form. Since that date the most 
important articles are as follows: 

Stand-pipe Failures at Elgin, Ill. Caused by ice. Eng. News, 1900, 
XLIII. p. 282. 

Stand-pipe Failure at Collingswood, N. J. Eng. Record, 1900, xli. * 
p. 58. 

Stand-pipe Failure at Garden City, Kan. Eng. News, Oct. 1, 1896, 
xxxvi. p. 218. 

15. The Compton Hill Masonry-enclosed Stand-pipe at St. Louis. Eng. 

News, 1898, xxxix. p. 206; Eng. Record, 1899, xl. p. 220. 

16. The West Arlington Stand-pipe, Baltimore. Masonry-enclosed. Eng. 

Record, 1899, xl. p. 413. 

17. New Water-tower at Schenectady, N. Y. Masonry-enclosed. Eng. 

Record, 1899, xxxix. p. 402. 

TANKS AND TOWERS. 

1. Intze. Description of Several Towers Built on the Intze System. Zeit. 

Ver. deutsch. Ing., 1886, xxx. p. 26. 

2. The Norton Tower of the Liverpool Water-works. The Engineer, 1892, 

lxxiv, supplement for July 15; Eng. Record, 1891, xxiv. p. 278; 
Proc. Inst. C. E., cxxvi. p. 24. 

3. The Water-tower at Worms, Germany. Eng. News, 1892, xxvn. p. 162; 

Eng. Record, 1892, xxv. p. 141. 

4. The Water-tower at Mannheim, Germany. Eng. Record, 1892, xxvi. 

p. 219. 

5. The Elevated Tank at Fairhaven, Mass. Eng. Record, 1894, xxix. 

p. 204. 

6. Flad. The Laredo Water-tower. Eng. News, 1894, xxxi. p. 206. 

7. Wooden Tank at Parkersburg, Iowa. Eng. News, 1895, xxxm, p. 34. 

8. The Fulda, Minn., Water-works. Wooden tower and tank. Eng. 

Record, 1895, xxxii. p. 438. 

9. The Scotland, Pa., Wooden Tank and Tower. Eng. Record, 1895* 

xxxii. p. 457. 

10. Steel Water-tower at Paris, Ill. Eng. Record, 1897, xxxv. p. 273. 


LI TER A TURE. 


681 

11. Tank of Monier Construction at Colbe, Germany. Zeit. d. Ver. deutsch. 

Ing., 1897, p. 301; Eng. News, 1899, xli. p. 87. 

12. Pressure Storage-tanks at Babylon and Southampton, N. Y. Eng. News, 

1897, xxxviii. p. 429. 

13. Fall of a Water-tower at Marshall, Minn. Eng. News, 1898, xxxix. 

p. 70. 

14. Marston. The Elevated Water-tank of the Iowa State Agricultural 

College. Eng. News, 1898, xxxix. p. 371. 

15. Snow. Steel vs. Wood Tanks (for railroad purposes). Jour. West. Soc. 

Engrs., 1899, iv. p. 268. 

16. Ellis. The Elevated Water-tank at Jacksonville, Fla. Eng. News , 

1899, xli. p. 258. 

17. Storage-tanks at Lacona, N. Y. Eng. Record, 1900, xli. p. 494. 

18. Water-tower at Murphysboro, Ill. Eng. Record, 1900, xlii. p. 6. 


CHAPTER XXVIII. 


THE DISTRIBUTING SYSTEM. 

738. General Requirements. — A distributing- system should be SO' 
designed that it will be able to supply adequate quantities of water to 
all consumers, and that this will be accomplished with economy and 
with reasonable security against interruption. With respect to the 
design of this part of a water-works system, the uses of water naturally 
fall into two very distinct classes: (1) the ordinary, every-day use for 
domestic, commercial, and public purposes; and (2) the use for fire 
extinguishment. In the former case the consumption is relatively 
uniform over different portions of the city, and is also well distributed 
over many hours of the day; in the latter case the rate is likely to be 
extremely high for a very short period of time, but this excessive use 
of water will usually be confined to a comparatively small area. To 
supply water in the former case requires the wide distribution of 
moderate quantities, while in the latter case the problem is rather the 
concentration of large volumes within a narrow district, which district 
may be situated at any point in the system. 

The cost of distributing-fnains is usually the largest item in the 
cost of a water-works, and consequently much care must be taken in 
the design of this part of the system. In small towns it will often be 
impracticable to provide as large mains as would be required to furnish 
entirely satisfactory fire protection, and in such a case the advantages 
of improved fire protection must be carefully balanced against increased 
cost of large pipes. 

To supply water to all consumers requires that a pipe be laid in 
each street, except in those cases where the cross-streets are not built 
upon. In the outlying districts, pipes are laid in those streets where 
the density of the population warrants it, according to the judgment of 
the management, but much difference in policy exists in respect to the 
matter of extensions. 

The distributing system includes, besides the pipes, the fire- 

682 


PRESSURE REQUIRED . 683 

hydrants, service connections, valves, fountains, watering-troughs, 
meters, and occasionally other details. 

739. The Pressure Required. — a. Ordinary Service .—For ordinary 
service the pressure at any point should be sufficient to supply water 
at a reasonable rate in the upper stories of houses and factories, and 
in business blocks of ordinary height. This will require at the street- 
level a pressure of from 20 to 30 pounds in residence districts, and 
usually from 30 to 35 pounds in business districts, according to the 
character of the buildings. 

b. Fire Service .—For fire purposes the pressure required in the 
mains depends upon whether it is intended that fire-streams shall be 
furnished directly from the hydrants or whether steam fire-engines are 
to be used. In small cities and towns it is of the greatest advantage 
to supply fire-streams without the use of engines, and in most such 
places this method is adopted, fire-engines being sometimes kept in 
reserve, however, for extraordinary conflagrations. In pumping 
systems the most common arrangement is to maintain only a moderate 
pressure for ordinary service, and at times of fires to shut off the reser¬ 
voir or stand-pipe if there be one, and to furnish the necessary fire- 
pressure direct from the pumps. In many plants, however, a good 
fire-pressure is maintained at all times, and this may be done without 
great expense if those buildings which demand the heaviest pressures 
are situated on the lower ground, and only scattered residences on the 
higher ground. Considerable economy is, however, usually secured 
by pumping against a low pressure except at times of fires. 

In large cities hydrant fire-pressure is not so common, but if the 
supply is by gravity, and has plenty of head, a hydrant fire-pressure 
can profitably be furnished, at least for all except the densest portion 
of the city or for very large fires. If the water requires to be pumped, 
then only the ordinary working-pressure of 25 to 40 pounds is usually 
provided, and dependence is placed on fire-engines to supply the 
deficiency. To furnish fire-pressure direct from the pumps at all times 
would, in the case of large cities, be very costly, and to increase the 
pressure at times of fires would be impracticable. 

If hydrant fire-pressure is to be supplied, it may be said that in 
general the pressures in the mains should be such and the hydrants so 
spaced that a large proportion of the fire-streams required in a business 
district should be of 240 to 250 gallons capacity, and in a residence 
district of 175 to 200 gallons capacity. If low hydrant pressures are 
furnished, the hydrants must be spaced closely, and if high pressures, 
then a wider spacing may be used. It will, however, be found that a 



684 


THE DISTRIBUTING SYSTEM. 


hydrant pressure lower than 60 pounds for residence districts and 70 
pounds for business districts will be undesirable, and that even these 
values will call for a close hydrant-spacing. Such pressures are, 
however, quite common. Much more preferable is a pressure of 80 to 
100 pounds, as this gives good streams with a reasonable hydrant¬ 
spacing. The lower limits of 60 to 70 pounds may then be accepted 
where a higher pressure cannot be furnished without a large extra 
expense, as in the case of many gravity systems; but where the 
pressure is furnished by pumps, and especially where high pressure is 
furnished only during fires, the expense of additional head is not great 
and the higher values of 80 to 100 pounds should be adopted. If 
steam fire-engines are used, then it is only necessary to supply water 
to the hydrants without risk of causing the fire-pumps to operate under 
suction. This low pressure may result in interrupting the supply for 
other purposes at times of large fires, but this would not be a serious 
matter. 

The pressures here considered are the hydrant pressures at times of 
maximum consumption, and refer to any point in the distributing 
system. If such pressures are maintained at the most remote points 
and at the higher elevations, the pressures on the lower ground and at 
points nearer the pumps or reservoir will of course be considerably 
higher. There will in general be certain critical points which will 
determine the pressures to be maintained at the source, and it will be 
a matter of economy to assume as low pressures as practicable for such 
points. 

The maximum pressures allowable in a pipe system is a question 
of expediency, in which increased cost of heavy piping and increased 
danger of breakage must be offset against any advantage derived from 
high pressures. With a pumping system this question would hardly 
arise, but with a gravity system supplied from an elevated source, the 
head available may be greater than is desired, either for the whole or 
a part of the area served, in which case some method of reducing the 
pressure for certain districts may be used (Art. 648). As will be seen 
from Table No. 96, the maximum fire-pressures in common use range 
from about 100 to 160 pounds, this referring to the pressures at the 
, pumping-stations. Generally speaking, pressures exceeding about 
130 pounds are found to give much extra trouble in breakages, and 
this may be taken as about the limit which it will not often be desirable 
to exceed for any considerable part of the distributing system. If the 
elevations of different portions of the town vary widely, then two or 
more zones of pressure may be used (Art. 751). 


PRESSURE REQUIRED. 


685 


In Table No. 96 are given the ordinary and fire pressures in the 
water-works of the United States, as stated in the Manual of American 
Water-works, 1888, and which serve to illustrate the practice in this 
respect. The pressures given refer usually to the pressures at the 
pumping-station, or in the principal mains, and hence are considerably 
higher than the effective pressures. 

TABLE NO. 96. 

AVERAGE WORKING- AND FIRE-PRESSURES IN I327 WATER-WORKS OF THE 

UNITED STATES. 

The table gives the number of works having the pressures indicated in the first column. 


Pressure per 
Square Inch, 
Pounds. 

1 

Average 

Working- 

pressure. 

Fire- 

pressure. 

Excess of Fire- 
over Working- 
pressure. 

Under 20 

16 


59 

20-29 

60 


57 

30-39 

122 


67 

40-49 

270 

9 

106 

50-59 

159 

II 

81 

60-69 

204 

27 

93 

70-79 

158 

36 

68 

80-89 

126 

73 

39 

90-99 

75 

70 

21 

100-109 

47 

M 3 

21 

110-119 

28 

32 

8 

120-129 

27 

99 

11 

130-139 

5 

30 

5 

140-149 

5 

23 

2 

1 5 o-i 59 

14 

54 

2 

160-169 

4 

13 

2 

170-179 

7 

11 


180-189 


3 


190-199 


3 


200 


11 



TABLE NO. 97. 

ESTIMATED NUMBER OF FIRE-STREAMS REQUIRED SIMULTANEOUSLY IN AMERICAN 

CITIES OF VARIOUS MAGNITUDES. 


Population 

of 

Community. 

Number of Fire-streams Required Simultaneously. 

Freeman. 

Fanning. 

Shedd. 

Kuichling. 

1,000.... 

2 to 3 

7 


3 

6 

5,000- 

4 to 8 


5 

6 

10,000... • 

6 to 12 

10 

7 

9 

20,000.. • • 

8 to 15 


10 

12 

40,000. . . . 

12 to 18 

14 

14 

18 

20 

60,000... . 

15 to 22 

17 

22 

100,000.... 

20 to 30 

18 

25 

22 

28 

34 




30 

38 

200,000. . . . 

30 to 50 



40 





44 





48 





































































686 


THE DISTRIBUTING SYSTEM. 


740. Number and Size of Fire-streams, —The number of fire-streams 

which should be simultaneously available in any given town will 
obviously vary greatly with the character of the buildings, width of 
streets, etc. This subject, together with other questions relating to 
fire-protection, has been thoroughly discussed in valuable papers by 
Mr. Freeman* and Mr. Fanning, + to which reference should be made 
for more detailed information. The general conclusions of these 
engineers as to the number of streams required, and similar estimates 
by Mr. Shedd and by Mr. Kuichling, are given in Table No. 97. { 
The values given by Mr. Kuichling may be expressed by the formula 

y = 2.8 Vx, 

where y — number of streams, and ;r = population in thousands. 

The figures given in the table relate to cities of average character, 
and are the total number of streams required simultaneously for the 
entire city. In regard to the actual number required at any one point 
Mr. Freeman estimates that as a general statement two-thirds of his 
estimated number should be capable of being “concentrated upon any 
one square in the compact valuable part of the city or upon any one 
extremely large building of special hazard. ” For compact residence 
districts one-fourth to one-half the number given in the table would 
usually be sufficient, and for small detached dwellings two to three 
good streams would answer. All these estimates should, however, be 
used with much caution, and should be varied to suit local conditions. 
Different large cities are likely to be of about the same general char¬ 
acter and the requirements will be similar, but in small cities and towns 
the requirements for fire-protection may differ widely. For example, 
in a country town of 4000 to 5000 inhabitants in which only a small 
mercantile business is carried on, the fire risk is not great, while in a 
town of the same size whose prosperity depends entirely upon two or 
three large factories, located, perhaps, in one large group of buildings, 
a fire would be a very serious matter. In the former case four or five 
fire-streams would be sufficient, while in the latter case eight or ten 
should be supplied. 

The number of fire-streams given in the table is based upon a size 
of stream of about 250 gallons per minute, which is generally consid¬ 
ered to be about right as an average value for good fire-streams in 

* Jour. A 7 ew Eng. IV. IV. Assn., 1892, VII. p. 49. 

f Proc. Am. W. W. Assn., 1892, p. 88; Eng. Nervs, 1892, July, p. 42. 

| From a paper by E. Kuichling in Trans. Am. Soc. C. E., 1897, xxxvm. p 15 




LOCATION OF HYDRANTS. 687 

business districts. For a residence district 175- to 200-gallon streams 
will usually meet the requirement. 

741. Location of Hydrants. —Fire-hydrants must be sufficiently 
numerous and so located as to meet the requirements regarding 
number and size of fire-streams set forth in the preceding article. 
Hydrants are one-way, two-way, three-way, etc., according to the 
number of hose-connections provided. For most purposes the two- 
way hydrant is considered the most convenient, but in the dense 
portion of a large city, where many connections must be provided, 
three-way and four-way hydrants can be used to good advantage. 
Hydrants should, in any case, be numerous enough to enable the 
required number of streams to be furnished with a suitable nozzle- 
pressure. At points where a large number of streams are required, 
fire-cisterns are sometimes used instead of hydrants. These cisterns 
are fed by large pipes, and have an advantage over hydrants in that 
they allow several steamers to obtain their supply at one point. 

For a 250-gallon stream the required nozzle-pressure is 45 pounds, 

. and the loss of head per 100 feet of ordinary 2j-inch hose is about 18 
pounds (see Table No. 50, page 240), so that with a hydrant pressure 
of 100 pounds the length of hose to supply a 250-gallon stream cannot 
exceed 300 feet. A 175-gallon stream, with a i-inch nozzle, requires 
35 pounds nozzle-pressure, and causes a loss of head of 9 pounds per 
100 feet of hose. With a hydrant pressure of 100 pounds the length 
of hose in this case might be 700 feet. With a hydrant pressure of 75 
pounds, which is quite common, a 250-gallon stream could not be 
supplied through a length of hose greater than about 200 feet, and a 
1 75-gallon stream through a length greater than about 450 feet.. 
Hence the general rule that hydrants should be so spaced that no line 
of hose should exceed 500 to 600 feet, and for at least half of the 
streams required at any point the length of hose should not exceed 
250 to 350 feet, according to the hydrant pressure. These lengths 
cannot be much increased even where fire-engines are used. In out¬ 
lying districts two two-way hydrants should be available at any point, 
with a distance of not more than 500 to 600 feet to the more remote 
of the two. 

The most convenient location for hydrants is at the street intersec¬ 
tions, as they are then readily accessible from four directions. In 
cities of moderate size the required number of streams can readily be 
supplied by locating a hydrant at each street intersection, but in large 
cities intermediate hydrants are often necessary. Thus if the blocks 
in Fig. 220 are 300 feet long in each direction, and a two-way hydrant 


688 


THE DISTRIBUTING SYSTEM. 


is placed at each corner, then a fire at A could be served from eight 
hydrants, with a maximum length of hose of 450 feet, giving sixteen 



T 

t 



V 

v / 

t 


t 

T 

t 

L 

t 

t 

T 


1 - 

1 

t 



r 

3 

T 



Fig. 22c 

>. 


Fig. 

22 T. 



good fire-streams; while a fire at a street-corner could be served from 
thirteen hydrants, eight of which would, however, require hose-lengths 
of 600 feet. With blocks 600 feet by 300 feet, as in Fig. 221, a two- 
way hydrant at each intersection would supply not less than eight 
streams at any point, without exceeding 600 feet of hose. If only four 
streams are required, then one-fourth of the hydrants might be omitted, 
or every other hydrant in alternate streets, as hydrants I, 2, and 3. 
This would just be within the requirement of a maximum hose-length 
of 600 feet. To omit half the hydrants, or to place them at one-half 
the intersections, would require the use of 750 feet of hose at certain 
points to supply two out of the four fire-streams. Such a spacing 
would therefore be inadequate. The necessary hydrant-spacing to 
furnish any given number of streams can be determined by the method 
here illustrated. 

742. General Arrangement of the Pipe System. —From the data of 

Chapter II (page 31) it is evident that the fire demand will largely 
govern in the design of the pipe system. This is more and more true 
the smaller the town or district considered, and for single blocks the 
ordinary consumption can practically be neglected. To supply long, 
narrow districts, the general scheme would be to furnish the water 
mainly through a single large pipe of gradually decreasing size, with 
small parallel and branch mains supplying the side streets, somewhat 
as in Fig. 228 (page 706), districts 1 and 3. For broad areas, such 
as comprise the larger portions of most cities, the general arrangement 
usually adopted is to provide large mains at intervals of \ to £ mile, 
and to fill in between these mains with smaller pipes, thus forming a 
gridiron system. The smaller pipes are designed with special refer¬ 
ence to supplying the fire-streams which are required at any point, 
without too great a loss of head, while the larger mains must be 
designed with reference to the ordinary consumption as well as to the 















GENERAL ARRANGEMENT OF THE PIPE SYSTEM. 689 

fire demand. The gridiron system is well illustrated by Fig. 222, 
which shows a section of the St. Louis distributing system. 

A general principle which should be kept in mind when laying out 
a system is to so arrange the large mains that the smaller cross-mains, 
may be fed from both ends, since a pipe so fed is equivalent to two 
pipes. It can furnish double the number of streams with the same loss 
of head, or the same number of streams with about one-fourth the loss 
of head, as when fed from one end only. This principle also makes it 
desirable to lay connecting pipes between separated districts, even 
when such pipes are not required for supplying local consumers. In 
the case of fire, each district may then be served from both ends. 
This plan is well illustrated in Fig. 228. In a gridiron system it is,, 
for the same reason, desirable to provide large mains near the outside 
edges of the network. Extensions will of course make it impossible 
to do this at all times, but the desirability of having a circulating 
system, and avoiding dead ends as much as possible, should be kept 
well in mind. Dead ends are also objectionable on account of the 
stagnation which exists in the pipes and the deterioration of the water 
which is likely to ensue. 

The size of mains and cross lines in the gridiron system will depend 
largely upon the number of fire-streams required at any point. In 
small cities, and outlying districts of large cities, 6-inch cross-mains 
with 8-, 10-, or 12-inch pipes at intervals of four to six blocks is a 
common arrangement. Four-inch pipe should rarely be used to supply 
hydrants. For compactly built districts many of the cross-pipes 
require to be 8 inches, and a more frequent use made of 12- and 
16-inch pipes. A good arrangement for a comparatively large demand 
is to lay 6-inch pipes lengthwise of the blocks and 8-inch pipes cross¬ 
wise. To supply large areas, still larger feeders, such as 24-, 36-, 
and 48-inch pipes, will be required. These are added to the system 
from time to time, as the needs of the city require and as the pressures 
become low through increased consumption. They should be so 
located and connected with the larger distributing-mains as to reinforce 

the pressure where most deficient. 

743. Maximum Rates of Supply for Different Areas. —For the pur¬ 
pose of calculating the distributing system it is necessary to know the 
maximum rate of consumption for the entire city, and for large and 
small sections of the same, with suitable consideration for future 
growth. The rate for the entire city will enable the main supply- 
conduit, or the principal force-main, to be determined. For calculat¬ 
ing the main distributing-pipes the city should be divided into 



THE DISTRIBUTING SYSTEM. 



Levee 























































































































MAXIMUM RATE OF SUPPLY FOR DIFFERENT AREAS. 69I 

relatively large districts, corresponding to the most probable location 
of such main arteries; then for the smaller pipes the demand for still 
smaller sections must be considered, and so on. 

1 he extent to which provision for future growth should be made 
will be different in the various parts of the system, and will vary 
according to circumstances. It will not usually be necessary to design 
for more than fifteen to twenty years in the future, and sometimes even 
for less. In making extensions, large mains can readily be added from 
time to time, and these can often be placed where no pipes now exist. 
A better pressure will eventually be furnished by several good-sized 
mains, placed some distance apart, than by one very large main. 
For small cities, where the fire demand is relatively large and does 
not increase rapidly with the population, a small increase in size of 
mains will make the system serviceable for a relatively long period in 
the future, and in this case twenty-five or thirty years’ growth might 
well be provided for. For that part of a system serving only a limited 
territory provision should be made for a fully built-up condition. 

The maximum rate of consumption for the entire city has already 
been discussed in Chapter II, page 31. From the data there given 
the ordinary maximum rate is seen to be from 200 to 250 per cent of 
the yearly average. If the yearly average be 100 gallons per capita 
daily, the maximum ordinary rate will then be about 250 gallons per 
capita per day, or 0.17 gallon per capita per minute. The maximum 
fire rate by Kuichling’s formula of Art. 740, assuming 250-gallon 
streams, is 250 X 2.8 Vx> — 700 Vx gallons per minute, where 4; = 
population in thousands. Thus for a population of 1000 the ordinary 
maximum rate may be about 170 gallons per minute, while the fire 
rate is likely to be 700 gallons, or four times as much. 

After estimating the maximum rate of consumption for the city as 
a whole, the same should be done for the several districts, the probable 
future population, the maximum ordinary rate, and the maximum fire 
demand being estimated for each district independently. The required 
number of fire-streams for the separate districts should be determined 
in accordance with the data previously given. In combining the con¬ 
sumption for two or more districts, the required fire supply should be 
found by considering the district as a whole and not by adding the 
separate requirements. The fire demand will increase but little as the 
size of district increases. 

To illustrate the points here considered, and other questions per¬ 
taining to the design of a distributing system, an arrangement of pipes 
will be assumed as shown in Fig. 228, page 706. This would be a. 


692 


THE DISTRIBUTING SYSTEM. 


suitable arrangement for the city of Madison, Wis., under certain 
assumed conditions which, for purposes of illustration, are different in 
some respects from the actual conditions. Pipes are shown where 
most needed, although there are a few more pipes actually laid than 
are shown. With respect to the natural conditions and the probable 
location of main arteries, the city may be divided into about ten 
districts as indicated. District No. 2 includes important factories. 
District No. 9 is a small suburb. The probable population fifteen tO' 
twenty years hence, immediately adjacent to the lines or which will be 
served by them, is assumed to be as given on the diagram; also the 
number of fire-streams simultaneously required in each district. The 
number for the entire city is taken at fifteen 250-gallon streams. The 
maximum rate of ordinary consumption is assumed to be 125 gallons 
per capita per day, the average rate at the present time being about 
45 gallons. The maximum rate of supply required for each district 
for ordinary and fire supply will then be about as given in Table 
No. 101, page 707. For districts Nos. 2 and 3 together the maximum 
rate would be 380 gallons per minute for ordinary consumption plus 
2000 gallons for fire purposes, = 2380 gallons per minute. Similarly, 
districts Nos. 4 to 10 would require altogether 2110 gallons for ordinary 
purposes, plus 15 fire-streams, or a total of 6560 gallons per minute. 
The calculation of the pipe system is further considered in Art. 750. 

A larger provision for the future than here made would probably 
be desirable for the main pipes in the vicinity of the pumping-station 
and in the denser portion of the city, as no additional lines of pipes 
would ever be needed here to supply the local demand. At outlying 
districts many streets remain unoccupied, which gives opportunity for 
enlarging the capacity when pipes are laid in these streets. 

744. Velocities of Flow for Fire Supplies. —In calculating a pipe 
system it is convenient to get first a good notion of the practicable and 
economical velocities which may ordinarily be used for the maximum 
fire draught. The most suitable velocities, or losses of head, will 
depend somewhat upon the system of supply, and also upon the loca¬ 
tion and elevation of the pipes in question. The various conditions 
will be included by considering the problem with respect to the follow¬ 
ing cases: 

(1) A pumping system in which fire pressure is constantly main¬ 
tained. 

(2) A pumping system in which fire pressure is maintained only at 
times of fires, the pressure at other times b~ing sufficient only for 
ordinary purposes. 


VELOCITIES OF FLOW FOR FIRE SUPPLIES. 


693 


(3) A gravity system with sufficient pressure for fire purposes. 

(4) A pumping or gravity system furnishing a low working-pres¬ 
sure only, fire-engines being used. 

(1) In this case if it be assumed that a certain minimum hydrant 
pressure is required at various points, this pressure, and the loss of head 
in the pipe system, will control the head against which the pumps 
operate; and as this head is constantly maintained, the disadvantage 
of small pipes and large frictional loss is very great. The best size of 
pipes, or the economical velocities, will in this case be different from 
those given in Chapter XXVI, page 552, but may be determined in a 
similar way. 

Let Q = average yearly rate of flow, or the average rate of con¬ 
sumption for any given district served by a given pipe. Let Q x — 
maximum rate of fire demand, plus the rate for ordinary purposes. In 
the case under consideration the pressure-head at the pumps will be 
determined by Q v but the actual yearly expense of pumping will be 
proportional to the volume Q , since the total amount pumped for fires 
is very small. We then have, as in eq. (5), page 550, 



.19 > 

d*~ 


and, as in eq. (6), the yearly cost = 

A = bsQ -f- 20 r -|- 2 ard 1,55 ' 

Substituting the value of differentiating, etc., as on page 551, we 
find that the economical velocity 


v 


30 


Q x ar 

Q ' b 


.36 


d’ 


27 


(o 


The economical velocity in this case is thus equal to the economical 
velocity for the average rate of consumption, as given on page 551, 

multiplied by [jk) , or approximately by the cube root of the ratio of 

the maximum to the ordinary rate. For small areas, such as two or 
three blocks, the maximum rate is likely to be fifty or more times the 
ordinary rate, but for areas consisting of several blocks the ratio is 
much less. Thus in the table on page 707, district No. 5, the ratio 
of the maximum to the average rate is about 12, and in No. 2 it is 
about 23, while for districts Nos. 4 to 10 combined it is only 4. 

To illustrate the variation in economical velocity with varying con- 





69I THE DISTRIBUTING SYSTEM. 


ditions, such velocities have been 

calculated for 

certain 

cases, 

taking 

the upper figures of Table No. 77, 

page 552, as 

a basis. 

The 

results 

are as follows: 







Ratio of maximum to ordinary rate. 

2 

4 

10 

25 

50 


6-inch pipe.. 

2.3 

3.0 

4.2 

5.8 

7-4 


8- “ “ ... 

2.5 

3.2 

4-5 

6.2 

8.0 

Economical velocities... « 

10- “ “ ... 

2.7 

3-4 

4-7 

6.6 

8.5 


12- “ “ ... 

2.8 

3-6 

5.0 

7.0 



[16- “ “ ... 

3 -o 

3-9 

5-4 




For still larger pipes the ratio will usually be quite small, and the 
velocities therefore not much greater than given in Table No. 77. 

(2) Where fire pressure is furnished only when needed, and a com¬ 
paratively low pressure is used at other times, the pipes are to be 
designed, first, to give economical velocities for ordinary service, and, 
second, to give practicable velocities and losses of head for fire service. 
It is desirable to limit the loss of head so that the fire pressure at the 
pumps will not need to be excessively high, both to avoid the use of 
extra thick pipe and heavy plumbing, and to avoid too large variations 
in the pump pressures. Ordinarily about 120 to 130 pounds is as high 
a pump pressure as is desirable to use, but sometimes a greater pressure 
is necessary to furnish fire-streams on the higher areas of the city. 
With a hydrant pressure of 80 to 100 pounds, and a pump pressure of 
120 to 130 pounds as a desirable maximum, the allowable velocities 
of flow will not much exceed those given in case (1), and may in fact 
be lower. The smaller mains would seldom be affected in any event, 
as a change of 2 inches in the diameter of a small main so greatly 
changes its capacity, but some of the larger mains might be reduced 
somewhat in size. 

(3) Where a gravity system furnishes a certain definite pressure at 
the distributing-reservoir, the loss of head allowable in the pipe system 
is more or less closely defined. If the available pressure is low, the 
distributing-pipes will need to be made large in order to obtain as 
much head at the hydrant as possible, but for certain areas and for 
large fires it may be cheaper to employ fire-engines than to go to a 
large expense to save loss of head in conduit and distributing-pipes. 
Where the available pressure is high, then the loss of head in the pipe 
system may equal the difference between this and a hydrant pressure 
of, say, 100 pounds. 

Whenever a certain definite loss of head is allowable between a 
reservoir and a certain section of the city, the proper distribution of 
this loss among large and small mains is a matter of considerable im¬ 
portance. A general solution of the problem will be of some aid. 







VELOCITIES OF FLOW FOR FIRE SUPPLIES. 


695 


In Fig. ■ 223, let d x , Q l , v 1 , /,, h l , and be, respectively, the 
diameter, discharge, velocity, length of 
pipe, loss of head, and hydraulic slope 
with respect to a main, AB; and 
let d 2 , Q 2 , etc., refer to corresponding 
quantities in a branch BC , of which * 4 Q. v 

A l /f S 

there are several of the same length 
and size. Let n = number of branches; 

H — total loss of head from A to C, 

• — /q -f- The total cost of the 

system is, by eq. (1), page 550, Fig - 22 3 - 



A — 20(/ 1 -f- nl 2 ) -f- 2 a(Jyd^’ ss -f- nl 2 d 2 - 55 ). . 


( 2 ) 


Substituting the value of d as derived from eq. (5), page 550, we have 


A — 20(/ 1 -f- nl 2 ) + 9 a[^ 


Gf 5 ^! 1 - 325 , 4 1,325 


/q* 325 


+ nQA 1 j 


•325 


(3) 


If we differentiate with respect to /q, or add an increment dh x , we at 
the same time subtract the same amount from /q, since /q -|~ /q = H = 
a constant. Hence o 7 q = — dh 2 . Differentiating then, and equating 
to zero, etc., we have for a minimum cost 


Qr 57 ^ 1 - 325 

/q x -3 2 5 


n 


g 2 - 57 4 ,,3as 


> 


or since, in general, 



we have 


or, practically, 






In the case where ?z< 2 2 = , or where all the branch pipes are dis¬ 

charging equally, then — = {^j ; that is, the hydraulic slopes for AB 

2 

and each of the branches BC should be as 1 : n \ Thus if a single 
large pipe branches into ten smaller ones, each designed to carry one- 
tenth the total volume, then the hydraulic slopes should be as 










696 


THE DISTRIBUTING SYSTEM. 


I : IO - 4 = I : 2 \. If four of the smaller pipes be designed to carry the 
entire volume, as for fire purposes, then Q 2 = \Q X , and we have 

_ / aQ \ \‘ 4 _ 

” WQJ ~ 3 - 6 ' 

The actual sizes of pipes for any given total loss of head and discharge 
can readily be found by trial by the aid of the diagram on page 233. 

The general principle here brought out is that in a distributing 
system containing a large number of small pipes, only a few of which 
are ever discharging at their full capacity at the same time, most of 
the loss of head at times of fires should occur in the near vicinity of 
the fire, and relatively little in the large mains leading thither. 

As already stated, the possible variation in size in the smaller pipes 
will be very little, but in the larger and more expensive mains con¬ 
siderable economy can be secured by a careful study of the problem, 
and by calculations of two or more possible arrangements. 

(4) Where a pressure sufficient only for ordinary purposes is pro¬ 
vided, the pipes must still be designed largely with reference to fire 
consumption, so that they will at all times be able to furnish full sup¬ 
plies to the fire-engines without suction. The problem is essentially 
the same as that discussed under (3). 

745. Loss of Head in Distributing-pipes, —To aid in the selection of 
the smaller sizes of pipes it will be convenient to tabulate the losses of 
head in such pipes, when supplying various numbers of fire-streams. 
Table No. 98 is made up in this way, the values given being based on 
the diagram of page 233. 

It will be readily seen that for any given number of streams the 
choice of pipe will usually be confined to two or possibly three sizes, 
since the loss of head varies so rapidly with change of size. The 
ordinary consumption may be neglected for short pipes supplying only 
one or two blocks, while for larger areas the ordinary rate may be 
converted into an equivalent number of fire-streams. 

For example, if ten streams are required, the choice would prob¬ 
ably be either a 12-, 14-, or 16-inch pipe. In the case of a city where 
12-inch pipes are used for comparatively short submains, such a size 
might be employed, but where serving larger districts, or where the 
available head is small, a 12-inch would be too small, and a 14- or 
16-inch should be used. The 16-inch pipe would probably be the best 
size if the district comprised a large portion of a small city, where the 
large main would be relatively long and the ratio of fire to ordinary 
consumption not very large. In the same way a supply of six fire- 



TABLE NO. 98. 

VELOCITY OF FLOW AND LOSS OF MEAD PER IOOO FEET IN DISTRIBUTING-PIPES WHEN DELIVERING GIVEN NUMBERS OF 

25O-GALLON FIRE-STREAMS. 

Loss of head, in feet, given by light-faced 4 pe. Loss of head, in pounds, given by bold-faced type. _ 


LOSS OF HEAD IN DISTRIBUTING-PIPES, 


697 


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698 THE DISTRIBUTING SYSTEM. 

streams would in most cases call for either a 10- or 12-inch pipe, and 
four streams an 8- or 10-inch, etc. It is to be particularly noted that 
a 4-inch pipe is hardly suited for even a single stream, and a 6-inch 
pipe for not more than two streams. 

The table and computations refer of course to the actual flow in the 
pipe. A pipe fed from both ends and supplying intermediate hydrants 
is equivalent to two pipes and should be so calculated. The diagram 
on which the table is based allows about 20 per cent increase in loss of 
head for corrosion, but in many cases a considerably greater allowance 
should be made for the smaller sizes, and unless it is quite certain that 
corrosion will not be great, 4-inch pipes should not be >’^ed at all to 

t 

supply hydrants. 

As it is frequently desirable to ascertain the size of a single large 
pipe equivalent to several small pipes, the relative discharging 
capacities of pipes of different sizes for the same loss of head are given 
in Table No. 99, the capacity of a 4-inch pipe being taken as 1. 

TABLE NO. 99 . 

RELATIVE DISCHARGING CAPACITIES OF PIPES FOR THE SAME LOSS OF HEAD. 


Size of pipe. 4 6 8 10 12 14 16 20 24 30 36 

Relative capacity. 1 3 6^ 12 20 30 43 80 130 235 390 


746. General Problems Pertaining to the Flow through Compound 
Pipes. —In calculating the flow through a system of pipes, several 
problems will arise. Some of these can be solved only by rough 
approximations, but there are two classes of problems for which simple 
general solutions can readily be found. Where a distributing system 
consists of but a few pipes, or is in the form of a long narrow district, 
the formulas derived can often be easily and directly applied. Where, 
however, the pipes spread over a broad area it is impracticable to- 
obtain anything more than a very rough approximation to exact 
results, but the general relations brought out by the solution of these 
two cases will assist in making reasonable assumptions in the more 
complicated case. 

The two general cases to be considered are: 

(1) The discharge from, or loss of head in, a single pipe-line of 

varying cross-section. 

(2) The discharge from, or loss of head in, a line of two or more 

pipes extending between any two given points. 

In both cases an algebraic expression could readily be derived 
giving the exact relation between discharge and loss of head, but prac¬ 
tically the problem is best solved by determining the size of a single 




FLOW THROUGH COMPOUND PIPES. 


699 

pipe which shall be equivalent to the given combination, that is, such 
a size as will give the same loss of head for a given discharge. The 
method of solution can best be explained by solving two examples. 

I. As an example of the first case let the sizes and lengths be as 
given in Fig. 224. To get the size c ^ n 

of a pipe 1600 feet long which will A 1 joo ' 1 too' 1 < 900 ' ^ 

give the same loss of head for the Fig. 224. 

same discharge, assume any convenient discharge, such as 400 gallons 
per minute. Then by the diagram on page 233 we have the following 
losses of head: 

For AC, loss = 120 X -3 = 36 feet 

“ CD, “ = 17 X -5 = 8.5 “ 

“ DB, “ = 4.5 X .8 ■= 3.6 “ 

Total loss of head = 48.1 feet 


The total loss of head is at an average rate of 30 feet per 1000. The 
size which will discharge 400 gallons per minute at this loss of head 
is then found by the diagram to be 5.3 inches in diameter, which size 
can be substituted for the given combination in all calculations relating 
to the section AB as a whole. 

2. In the other case assume the arrangement shown in Fig. 225. 
The problem is to get the size of a single pipe from A to B, equivalent 

to the given combination. Get first, 
by the method just described, the size 
of a uniform pipe ACDB, 1200 feet 
long, which shall be equivalent to the 
pipes A C D B as shown. This size will 
s be 4.5 inches. Now the loss of head 
Fig. 225. between A and B must be the same by 

both routes. Assume any loss of head, as 10 feet, and find the dis- 

10 

charge by each route. For the 6-inch pipe the loss is -g = 16.7 feet 


c 


* 


D 



600' 



6* 


600' 

■N 

6' 


per 1000 feet, and the discharge = 390 gallons per minute. For the 

10 

4.5-inch pipe 1200 feet long the loss is — = 8.33 feet per 1000, and 

the discharge = 130 gallons per minute. The total discharge = 520 
gallons, and the size of pipe 600 feet long which will deliver 520 
gallons at a loss of head of 10 feet is found to be about 6.7 inches, 
which is the equivalent size desired. If three or more pipes extend 
from A to B, the problem can be solved in a similar manner. Where 









700 


THE DISTRIBUTING SYSTEM. 


the pipes are of the same length the relative discharges can be deter¬ 
mined from the table of relative capacities on page 698. 

In practice there will usually be complications from the fact that 
two routes may be connected at more than two points, in which case 
no simple exact method of calculation can be used; but by making 
certain reasonable assumptions as to the direction of flow, and eliminat¬ 
ing some of the cross-connections, the problem may be reduced to the 
simple form just discussed. A more extended example is given on page 
708. In making assumptions as to the relative flow in different lines, 
there should be kept in mind the very great effect of diameter (about 
as d *) and the comparatively small effect of distance (about as VI). 

747. Calculation of the Pipe System. —Before beginning the calcula¬ 
tion of a distributing system, a map should be prepared showing thereon 
the streets where pipes are required, probable lines of future growth, 
character of buildings in various districts, etc. On the map can also 
be recorded the population of various districts, ordinary rates of con¬ 
sumption, and number of fire-streams required simultaneously at 
different points. There should also be shown on this map the desired 
hydrant pressure at various points, referred to a horizontal plane as 
well as to the ground-surface. This pressure will of course be selected 
with reference to the head available, and may need to be altered before 
the plans are finally completed. 

In designing a pipe system it will be well to first lay out in a tenta¬ 
tive way certain main lines of pipes, or arteries, to supply certain large 
districts, which may be more or less separated by undeveloped territory. 
Then it will be convenient to determine upon the size and arrangement 
of the smallest cross-mains, according to the number of fire-streams 
needed in any given small area. The arrangement of submains feed¬ 
ing these smaller ones, and connections with the main arteries and the 
submains in other districts, can then be arranged, provision being 
made at all points for the ordinary consumption as well as the fire 
supply. Then, with a tentative plan, the maximum number of fire- 
streams should be assumed in use at various points in the system, and 
the loss of head between the source and the hydrants in question 
estimated as closely as practicable. This loss should not exceed the 
desired limit, and for economy should be adjusted in accordance with 
the principles of the preceding articles. Several arrangements should 
be tried and comparative estimates made. As already shown, the 
possible variations in size will not be large. 

The calculations involved will be only roughly approximate, and to 
enable them to be made at all, certain assumptions may be necessary 


CALCULATION OF THE PIPE SYSTEM. 


701 


as noted in the preceding article. If the area is broad, the calculations 
are much more difficult than where it is long and narrow. It is to be 
noted that any large system will be built up gradually, and will have 
to be reinforced from time to time by additional larger mains or by 
replacing small ones by large ones. The actual loss of head which 
obtains may then be known by actual measurements, and the effect 
of additional mains can be quite easily estimated. However, in laying 
out new systems, and often in investigations of old systems, certain 
calculations need to be made. 

748 . Calculation of Small Service Mains .—In long narrow districts 
the pipes can be calculated by the methods already described, but 
where the system covers a broad area the problem is a very indefinite 
one. In such a case we will usually have, as noted on page 688, a 
general scheme of large pipes filled in between with smaller pipes, 
forming a sort of gridiron system. 

The size and arrangement of the small mains can be determined 
conveniently by the following approximate method: In Fig. 226 is 
represented a system of small cross-mains 

where the streets are 250 to 300 feet apart- .• —- 

in each direction. It is assumed that the 

pipes are fed from both directions. Sup-- f -t ' 

pose it is desired to concentrate 20 fire- i hi \ 

streams at A without exceeding 600 feet-y ~f 

of hose, assuming that the hydrants are 

suitably spaced to render this possible. .7 

Draw a circle with a radius of about 500 

feet with A as a center. It will be found | 7 ~ 

to cut fourteen lines of pipe. It will then p IG# 226< 

be approximately correct to assume these 

fourteen lines of pipe tributary to the fire, without reference to the 
exact location of the hydrants. Each pipe where cut by the circle will 
then on the average have to supply 1.7 fire-streams, or 420 gallons 
per minute, and if 6-inch pipes be used, the loss of head at this point 
will therefore be about 20 feet per 1000 feet, assuming all pipes to dis¬ 
charge at the same rate. This assumption will be approximately 
correct for a small area situated in a large system and surrounded by 
large pipes, as the loss of head near the fire will be much gieatei than 
at points more remote. The loss of head at points nearer A will be at 
a rather less rate than at the given circle, if the hydrants be evenly 
distributed ; and the loss of head outside this circle will rapidly decrease 
as other vertical and horizontal lines are crossed. 


0-3 00 


Fig. 226. 


















702 


THE DISTRIBUTING SYSTEM. 


If thirty streams were needed in the same area, each pipe would 
have to supply 2.1 streams, or 520 gallons. If 6-inch pipes be used, 
the loss of head would be about 28 feet per 1000, which might be a 
greater loss than desirable. In this case the supply could be furnished 
by the use of 8-inch pipes running one way and 6-inch the other. 
Then at least six 8-inch pipes would be available, and eight 6-inch.. 
By the table on page 698 it is found that six 8-inch pipes are equiva¬ 
lent to thirteen 6-inch pipes, hence we have an equivalent of twenty- 
one 6-inch pipes, giving a loss of head of about 14 feet per 1000. In 
this case every alternate pipe might perhaps be made an 8-inch. For 
still larger supplies all pipes can be made 8-inch, or a 10- or 12-inch 
pipe placed in every second or third street. In general it is somewhat 
more economical to provide volume in one or two large pipes than to 
increase the size of all, but care should be taken that the smaller pipes 
are not too long for the number of hydrants placed upon them. 

The approximate loss of head, locally, can be found in the way 
described for any given arrangement, where the location is in the cen¬ 
tral part of a large network of pipes or where large pipes surround the 
territory. 

For residence districts the blocks are usually about 250 to 300 feet 
by 500 to 600 feet, and larger pipes must be used to furnish the same 
number of streams with the same loss of head. 

To aid in estimating the value of any particular arrangement of 
cross-mains, the approximate number of fire-streams which may be 
supplied by different arrangements of pipes at a loss of head of about 
10 pounds for the first 1000 feet from the center, is here given. 


TABLE NO. 100 . 


APPROXIMATE NUMBER OF FIRE-STREAMS SUPPLIED BY DIFFERENT ARRANGEMENTS 
OF PIPES FOR A LOSS OF HEAD OF IO POUNDS IN FIRST IOOO FEET. 


Arrangement of Pipes. 

Blocks 300 feet by 600 feet. 

All 4-inch. 

4-inch lengthwise, 6-inch crosswise. 

All 6-inch. 

6-inch lengthwise, 8-inch crosswise. 

All 8-inch... 

6-inch lengthwise, 10-inch crosswise 
6-inch lengthwise, 12-inch crosswise 
Blocks 300 feet by 300 feet. 

All 4-inch. 

4-inch and 6-inch. 

All 6 inch. 

6-inch and 8-inch. 

All 8-inch. 

6-inch and 10-inch. 


Approximate No. 
of Streams. 

. 6 

. 10 

. 20 

. 25 

. 40 

.40 

.50 

. 9 

. 18 

.25 

.40 

. 60 

. 65 















CALCULATION OF I'he pipe system. 703 

The loss of head here considered refers to the most centrally 
located hydrant; the loss at other hydrants will be less. In many 
cases a considerably larger loss than here given would be permissible, 
and the possible number of fire-streams could be increased, but not 
often more than 25 per cent. 

749. Calculation of Large Mains. — The arrangement of mains and 
submains must be made with reference to the ordinary consumption 
as well as the fire demand, and proportioned in accordance with the 
principles already discussed. The best velocities will be much lower 
than in the small pipes. If nothing but fire demand existed, an ideal 
system would consist of a network of pipes of the sizes determined in 
the last article, surrounded by a large feeder so as to maintain a nearly 
uniform pressure at the periphery. The water could then be concen¬ 
trated for fire purposes with the least loss of head, and no other large 
mains would be required. But to provide adequate pressure over large 
areas the ordinary consumption must be taken account of. A certain 
number of large mains will be required, and these will increase in size 
as we approach the source of supply. It is in these large mains and 
branches that a great saving can be effected by having two or more 
reservoirs located at different points in the city. The possibility of one 
of the large mains being shut off in time of fire should be considered, 
and the system so arranged that the small mains may be fed from two 
or more larger ones. 

Let Fig. 227 represent a part of a large network of pipes, in which 
the lines AB and BC are at or near margins of the system. With the 
arrangement shown let it be required to determine approximately the 
maximum loss of head between D and any other point, such as Z, in the 
section EH, and to adjust the size of the large mains. Suppose that 
twenty fire-streams, or 5000 gallons per minute, are required in the 
vicinity of Z, and, further, that the maximum rate of the ordinary con¬ 
sumption is 400 gallons per minute in each of the large divisions. 

With twenty fire-streams in action near Z, the loss of head in the 
6-inch pipes between Z and the surrounding large pipes will be found 
to be about 10 pounds, although the pressures in these large pipes will 
vary considerably at different points. The line EB feeds five 6-inch 
pipes, three of which are likely to be called upon simultaneously to 
supply about two fire-streams each; hence EB would have to supply 
about six streams. From the table on page 697, we would evidently 
need about a 12-inch pipe, and this is the size which would result by 
the application of the method of Art. 744. BH will also be made a 
12-inch pipe. Of the twenty fire-streams demanded at Z, six or eight 


THE DISTRIBUTING SYSTEM. 


704 

may be assumed to come from GH together with the five 6-inch pipes 
between GH and jk-- The line GH will also partly supply SH } and 
as the capacity of five 6-inch pipes is not much more than one 10-inch, 



we may assume that five or six streams will be carried by GH. This 
line will then need to be again a 10- or 12-inch pipe. 

Farther away from ^ the proportion carried by each large main 
becomes very difficult of estimation. In the arrangement here assumed 
the small pipes have about one-half the capacity of the large ones, 
except in the vicinity of D. It will be reasonable, then, to design the 
large pipes to carry two-thirds of the total required quantity, and to 
provide for contingencies by assuming at the same time one of the 
large pipes tributary to any district to be out of service. Another 
method which may be used is to assume all the water carried by the 
large pipes, leaving the contributions of the smaller pipes as a margin 
of safety. Whichever assumption be made, the approximate loss of 
head in the large mains from Z towards the source D can then be 
found in the same general way as employed for service-mains. To do 
this we may sketch the lines ab, cd , etc., across the system in such a 
direction that they will represent, as nearly as can be judged, lines of 














































CALCULATION OF THE PIPE SYSTEM. JO 5 

equal pressure; then note the number and size of large mains cut by 
these lines. The relative flow in each main can then be estimated in 
proportion to its capacity and the directness of the route, and the 
approximate loss of head per 1000 feet determined at several points, 
and finally the total loss between Z and D. The maximum rate of 
the ordinary consumption should be taken account of at each section. 
Very roundabout routes should be omitted from the calculation, and a 
margin allowed for contingencies in one of the ways mentioned above. 

The loss of head between iT and D may in the present case be 
estimated as follows: On section ab the rate of flow is about 5700 
gallons per minute, two-thirds of which is 3800 gallons. Four 12-inch 
pipes are intersected, and, omitting one for contingencies, the flow 
through each of the others will average about 1300 gallons per minute, 
which will give a loss of head of about 5 feet per 1000. For section 
cd the maximum rate will be about 6800 gallons, with about four pipes 
available for two-thirds this amount, which will involve a loss of head 
of about 3.8 feet per 1000. Similarly on section ef the volume is 
about 8500 gallons, with four pipes in service, giving a loss of head of 
5.5 feet per 1000. On section gh we will assume available for the total 
volume, one 20-inch pipe, one 16-inch, and seven 6-inch pipes. The 
volume equals about 9600 gallons per minute. The loss of head for 
this combination is about 5 feet per 1000. Farther towards D the 
supply may be assumed to come through the 20-inch pipe and one 
16-inch, which will also give about 5 feet loss of head per 1000 feet. 
In the 24-inch supply-pipe, with a rate of 98,000 gallons per minute,, 
the loss of head would be about 6 feet per 1000. 

Considering the average distance traveled from section to section,, 
assuming blocks 300 by 600 feet, the actual loss of head from ab to cd 
is approximately 8 feet, from cd to ef 8.5 feet, from ef to gh 5 feet, 
and from gh to D 4.5 feet. Adding the loss of head in the small pipes 
and mains near Z', we find a total loss of head of 50 to 55 feet, or 
about 23 pounds, which would ordinarily be a reasonable allowance. 

With a reservoir at A, or beyond, nearly all the 12-inch submains. 
could readily be reduced to 10-inch or 8-inch pipes, or perhaps' most 
of them to 6-inch. The volume flowing through any pipe would be 
reduced about one-half, and the distance traveled also about one-half, 
thus reducing the loss of head very greatly. A large main of about 
20 inches in diameter, extending from pumps to reservoir, would, 
however, be required. 

750. Example .—In Fig. 228 is shown a possible arrangement of pipes and 
hydrants to meet the conditions stated on page 692 and in Table No. ion 


7q6 


THE DISTRIBUTING SYSTEM. 



Fig. 228.—Example of a Distributing System. 




















































CALCULATION OF THE PIPE SYSTEM. 


707 


A considerable use is made of 4- inch pipe, as experience has shown that well- 
coated pipe will corrode very slowly with the Madison water. The fire-pres- 

TABLE NO. 101 . 

ESTIMATED POPULATION, AND MAXIMUM ORDINARY AND FIRE-RATES FOR 

DIFFERENT DISTRICTS OF FIG. 228. 


District. 

Estimated 

Future 

Population. 

Maximum 
Ordinary Rate, 
Gallons per 
Minute. 

Maximum 
Fire-rate, 
Gallons per 
Minute. 

Total Maxi¬ 
mum Rate, 
Gallons per 
Minute. 

I. 

3900 

340 

800 

II40 

2. 

800 

90 

2000 

2090 

3 . 

34OO 

290 

800 

IO90 

4 . 

3500 

300 

2500 

2800 

5 . 

2500 

220 

2500 

2720 

6. 

5300 

460 

2500 

2960 

7 . 

3400 

300 

1200 

1500 

8. 

3400 

300 

1200 

1500 

9 . 

1600 

140 

800 

940 

10. 

4500 

390 

2500 

2890 

Entire city... 

32300 

2830 

3750 

6580 



sure at the pumping-station is assumed to be 120 pounds, and the pipes made 
of such size that the loss of head to the most remote hydrant will not exceed 












































THE DISTRIBUTING SYSTEM . 


708 


40 pounds. The ground is assumed to be level. Many other arrangements 
could be made, some of which might be more economical than that given. 

As a further example of the application of the method of calculation given 
in Art. 746, page 698, we will here compute the approximate loss of head 
from the pumping-station A, Fig. .228, to the point B, where it is assumed 
that eight fire-streams are in use. We will for the present neglect the ordinary 
consumption and, to make the solution possible, will omit certain cross-lines 
and modify the arrangement as shown in Fig. 229. We will also estimate 
that the various pipes from a to b are equivalent to a single 12-inch pipe. 
The problem is to determine the loss of head from the pumps to the point / 
by finding the size of a single pipe which will be equivalent to the system 
shown. The blocks of Fig. 228 are assumed to be 600 feet long by 300 feet 
wide. Beginning with the loop hki we first find a single pipe, hi, equivalent 
to the two pipes showm, then a single pipe ef equivalent to the given pipe ef 
together with the new pipe egif just found, etc. The calculations are very 
quickly made as shown in Art. 746. The results in detail are as follows: 


Line. 

Diameter. 

Length. 

hi 

6 

1200 } 

hjki 

4 

1800 f 

egh 

6 

1870 \ 

Equiv. hi 

6-5 

1200 >■ 

if 

6 

300 ) 

Equiv. ehf 

6.2 

3370 ) 

e f 

4 

3000 f 

ce 

6 

370 j 

Equiv. ef 

6.7 

3000 >• 

fd 

6 

300 ) 

cd 

8 

3600 ) 

Equiv. cefd 

6-5 

3670 j 

ab 

12 

1800 ' 

be 

10 

980 

Equiv. cd 

9-5 

O' 

0 

0 

dl 

8 

1500 J 

nqp 

6 

3300 ) 

nop 

6 

2100 ) 

amn 

6 

3000 \ 

Equiv. np 

7-4 

2100 j- 

ps 

6 

300 ) 

Equiv. ans 

6.4 

5400 ^ 

ars 

8 

4 SOO J 

Equiv. as 

9-3 

4800 ) 

si 

8 

300 j 

Equiv. abl 

9.4 

7880 ) 

Equiv. asl 

9.2 

5100 j 


r 

Line. 

-Equivalent Pipes.- 

Diameter. Length. 

hi 

6-5 

1200 

ehf 

6.7 

3370 

e f 

6.7 

3000 

cefd 

6-5 

3670 

cd 

9-5 

3600 

abl 

9.4 

7880 

np 

7.4 

2100 

ans 

6.4 

5400 

as 

9-3 

4800 

asl 

9.2 

5100 

al 

11 -3 

5100 


Thus the system all is equivalent to a single pipe 9.4 inches in diameter 
and 7880 feet long, and the system asl is equivalent to a 9.2-inch pipe sioo 
feet long. Finally, these two are found to be equivalent to a single pipe 11 , 
inches in diameter and 5100 feet long. The loss of head in such a pipe 
for eight streams of 250 gallons each, would be 13.6 feet per 1000, or a total 
loss of about 70 feet or 30 pounds. The volume carried by the system all 





SEPARATE SERVICES POP DIFFERENT ELEVATIONS . ? Og . 

will be equal to that which would be carried by a 9.4-inch pipe 7880 feet 
long, with a loss of head of 70 feet. This will be about 900 gallons per 
minute. 1 he volume carried by the other system will be 1100 gallons per 
minute. Corrections can be approximately made for the amounts consumed 
locally by adding such amounts to the above quantities at a few points along 
the pipe system. 

751. Separate Services for Different Zones of Elevation _Where the 

different parts of a town vary considerably in elevation, it is frequently 
advisable to divide the distributing system into two or more independ¬ 
ent portions, each serving an area or zone situated between certain 
limiting elevations. It often happens that only a small portion of a 
city is at a high elevation, and by thus separating the systems of dis¬ 
tribution a comparatively small amount of water will need to be raised 
to the maximum height, the greater portion being pumped against a 
much lower pressure. By this arrangement a large saving can be 
effected in the expense of pumping, and the use of excessive pressures 
in the lower districts will also be avoided. 

Various arrangements may be made for supplying the different 
zones. Each zone may be practically an independent system, with its 
own pumping-station and perhaps its own source of supply; or the 
pumps of a higher zone may be supplied by a reservoir located at a 
high point in the next lower zone; or the pumps of the different zones 
may all be located at the same station and obtain their supply from 
the same source. In the gravity system a division is often made so 
that the lowest zone is supplied by gravity, while the upper zones are 
supplied by pumps. The most favorable arrangement will be deter¬ 
mined chiefly by the cost of operation and the cost of the necessary 
piping. For small plants separate pumping-stations would rarely be 
an economical arrangement. Separate pumps placed in the same 
station would probably be employed; or, where the difference in pres¬ 
sure is not great, the same pump may be designed to supply the two 
services alternately. The latter arrangement will require some 
storage capacity in each system. 

The advantage of two or more services depends largely on how 
great a proportion of the supply can be furnished at the lower pressure. 
If any considerable amount of storage is provided in the higher of two 
systems, advantage may be taken of this to furnish water at a high 
pressure for fire purposes in the lower system. For this purpose, con¬ 
nections controlled by suitable valves should be made between the two 
systems at one or more points. If the lower system contains a reser¬ 
voir, it can be shut off in the same way as described for stand-pipes 
(page 661). 


710 THE DISTRIBUTING SYSTEM . 

Separate systems for different pressures have a disadvantage in the 
fact that at their margins the two networks of pipes are not connected, 
and, as a result, somewhat larger pipes are required for the same 
efficiency than in the single system. 

752. Location of Pipes and Valves. —The distributing-pipes should 
be so located with respect to street lines as to be readily found and to 
avoid other structures as far as practicable. The center of the street 
being usually reserved for the sewer, the water-pipes are placed at 
some fixed distance, usually from 5 to 10 feet, from the center. The 
side chosen should be the same throughout. The north side of east 
and west streets will be warmer than the south side. 

Valves should be introduced in the system at frequent intervals so 
that comparatively small sections can be shut off for purposes of 
repairs, connections, etc. As a general rule, wherever a small pipe 
branches from a large one, the former should be provided with a valve. 
Thus with 10- or 12-inch pipes feeding 6-inch pipes, each of the latter 
should have a stop-valve at each end. At intersections of large pipes 
a valve in each branch is usually desirable. In a network of small 
pipes of uniform size, a valve in each line at each intersection, or four 
in all, is rather more than necessary, but two at each intersection, or a 
valve in each line every two blocks, answers very well. The map 
of Fig. 228 shows a suitable arrangement of valves for the case in 
question. 

Valves, like pipe-lines, should be located systematically. They 
are usually located in range either with the property-line or the curb¬ 
line, but sometimes are placed in the cross-walks. A form of three- 
way and four-way valve, placed at the intersection of two pipes, has 
been used to some extent. This arrangement reduces the number of 
valve-boxes and is reported to be quite satisfactory. 

753. Hydrants. —The general location of hydrants has already been 
considered in Art. 741. In fixing upon the exact location, and the 
side of the street on which each should be placed, a detailed examina¬ 
tion should be made and the location determined with reference to 
important buildings, convenience of access in case of fires, etc. 
Generally the hydrant is placed on the same side of the street as the 
pipe, and is connected to the larger of two pipes where there is a 
choice. 

Hydrants are of two general types: the post hydrant, in which the 
barrel of the hydrant extends 2 or 3 feet above the ground-surface, 
and the flush hydrant, in which the barrel and nozzle are covered by 
a cast-iron box flush with the surface. The former is more commonly 


HYDRANTS. 


7 ir 


used, and as it is much more readily found and more conveniently 
operated, it is to be preferred, except perhaps in the congested districts 
of large cities, or on narrow streets where all obstructions should be 
avoided. Post hydrants are set just back of the curb-line; flush 
hydrants, either in the sidewalk or in the street. In Boston and some 
other Eastern cities, extensive use is made of a flush hydrant placed 
directly over the main, or at the intersection of two mains. 

The branch supplying the hydrants should be of a size correspond¬ 
ing to the number of streams to be carried, and should be designed on 
the same principle as other pipes. For one fire-stream the branch 
may be 4-inch, and for two streams 6-inch, etc. The hydrant-barrel 
should be nearly as large. 

Many styles of hydrants are on the market, most of which will give 
reasonably good service if properly handled. Reliability of operation 
is the first essential, but next in importance is the requirement that the 
frictional loss in the hydrant shall be small. All waterways should 
be ample, and sharp angles and sudden changes in size should be 
avoided as much as possible. Considerable difference exists in differ¬ 
ent hydrants in this respect, with a corre¬ 
sponding difference in the amount of 
pressure lost.* The main valve, which 
is located at the base of the hydrant, 
should seat accurately and remain tight, 
and when open should provide ample 
waterway. Valve-stems should be made 
of extra strength, as they are likely to be 
subjected to rough usage. Valve and 
stem should be removable without the 
necessity of digging up the hydrant. In 
Fig. 230 are shown two forms of hydrants 
which illustrate the two general types of 
valves used, —the gate-valve and the 
compression-valve. Small independent 
valves controlling the nozzles are useful in 
multiple-nozzle hydrants, as they enable 
hose-connections to be more conveniently 
made. In ordering hydrants care should 
be taken to have the nozzles of the same 
standard as those used in adjoining large 



Fig. 230.—Fire-hydrants. 


* See results of experiments on hydrants by Newcomb in Trans. Am. Soc. M. E., 
1899, XX. p. 494- 


























































































712 


THE DISTRIBUTING SYSTEM. 


cities, so that connections can readily be made to fire apparatus which 
may be borrowed in emergencies. 

When a hydrant is closed after use, the water remaining in the 
barrel must be drained out through a drip, so arranged as to open 
when the main valve is closed. This is an important feature of the 
design, as a hydrant is likely to freeze if not thoroughly drained. The 
escaping water may be led away through a small drain-pipe to a 
sewer, or a considerable body of broken stone and gravel may be filled 
around the base, into which the water may be allowed to drain. If 
the hydrant base is below ground-water level, the drip should be 
plugged and the hydrant pumped out after use. Hydrants are fre¬ 
quently provided with an outside shell or frost-case, but the use of this 
has been found of little advantage. In setting hydrants care should 
be taken to provide a firm base and to ram solidly back of the barrel. 
The hydrant branch should be covered at least as deep as the main, 
as this branch is essentially a dead end and is much more likely to 
freeze than the main itself. 

754. Depth of Covering for Distributing-pipes. —In constructing the 
pipe system one of the most important points to settle is the depth at 
which the pipes should be laid. In warm climates a covering of 2 to 
3 feet is sufficient. In cold climates the depth to be adopted is that 
which will be sufficient to prevent freezing. In the Northwestern 
States the common practice of a depth of 5 to 6 feet proved insufficient 
during the severe winter of 1898-9, and many small mains as well as 
service-pipes froze. The experience at that time indicated that in this 
region 7 feet should be about the minimum for small pipes. In a 
general way it may be stated that in New York and New England the 
depth of cover should be 4 to 5 feet for latitude 42 °, and 6 to 7 feet for 
latitude 45 °. Between Lake Michigan and the Rocky Mountains the 
corresponding minimum depths should be not less than the larger of 
these figures. In sandy soil the depth should be a maximum. Large 
pipes are not likely to freeze, but should be placed at about the same 
depth as the smaller pipes to aid in maintaining the water above a 
freezing temperature. 

755. Service Connections. —Service-pipes are usually from f inch to 
1 inch in diameter. The question of the most suitable material for 
these pipes has been discussed in Chapter XXIV. In makin O' the 
connection between service-pipe and main, the latter is tapped and a 
brass “corporation” cock screwed in. This cock is then usually 
connected to the service-pipe by means of a goose-neck, or U-shaped 
piece of lead pipe, in order to avoid breakage from settlement of 


SPECIAL FIRE-PROTECTION SYSTEMS. 


/I3 


main, although this detail is omitted by some, with apparently no 
bad results. At the curb is usually placed another stop-cock, with 
a suitable valve-box, at which point the supply to the consumer is 
controlled. Service connections can be made without shutting off the 
water, by the use of special tapping-machines, several of which are on 
the market. 

756. Other Details. —In laying out lines of pipe, small depressions 
should be avoided, but as a rule the line may follow the street grade 
closely. Hydrants can usually be placed at low and high points and 
thus can act in a measure as blow-offs for clearing out sediment, and 
as air-valves. For draining large mains, small drain-pipes connecting 
with the sewer should be constructed at the lower points of the system. 

The construction of the pipe-lines has already been described in 
Chapter XXV. Where pipes are laid in city streets, special care must 
be taken in backfilling and replacing the pavement. There is a wide 
difference of opinion as to the best method of backfilling, but probably 
tlie most certain way of getting the earth back without trouble from 
future settlement is by very thorough ramming of the material in a 
moist condition, but not wet. Such thorough ramming is difficult to 
secure, and it will usually be advisable to adopt the method of backfill¬ 
ing through a good depth of water. Hydrants are often deranged by 
being used for filling sprinkling-carts. It is much preferable to provide 
water-cranes for this purpose, numerous forms of which are on the 
market. 

757. Special Fire-protection Systems — In several cities located on 
bodies of water, the fire service has been largely reinforced in certain 
districts by special fire pipe-lines, leading from the water-front and 
supplied with water by means of powerful fire-boats. These boats are 
in general use in large cities for fighting fires along the shore and 
among the shipping, and by laying special lines of pipe of compara¬ 
tively short length, they can be made of great use in fighting fires 
farther inland. They are usually of large capacity,—equal to from 
ten to thirty fire-engines,—and so can supply very large and efficient 
fire-streams. By means of telephonic or telegraphic communication, 
one fire-boat can serve any one of several pipe-lines. Connections 
between boat and pipe-line are made by means of several lines of hose. 
Very high pressures can profitably be employed in these systems, and 
this requires that the pipe-lines and all details be specially designed. 
The hydrants should be of large size. No connections other than to 
hydrants should be allowed. Generally these lines are emptied after 


7*4 


THE DISTRIBUTING SYSTEM. 


fires, and consequently they must be provided with ample air- and 
waste-valves, and often with relief-valves. 

Where salt water is used in such systems, special care must be taken 
in the design of valves, etc., to avoid the combination of dissimilar 
metals without insulation of rubber or other like material. Otherwise 
galvanic action will be set up and rapid corrosion will result. Besides 
this feature, and the slightly increased rate of corrosion of pipes, there 
is no objection to the use of salt water. 

Special fire pipe-lines of the kind here described are in use in 
Cleveland, Milwaukee, Detroit, Buffalo, and Boston; and the experi¬ 
ence of these cities shows the system to be a very efficient method of 
affording increased fire protection. In Milwaukee there were, in 1900, 
about 8 miles of special pipe-lines, 164 hydrants, and 3 fire-boats, 
each of 6000 gallons capacity. At Detroit there are about 5 miles of 
lines served by one boat.* At Providence, R. I., a special system of 
mains has been constructed in the center of the business district for fire 
purposes only. The supply in this case is taken from the main leading 
from the high-service reservoir. The pressure on the hydrants is from 
85 to 116 pounds, static. The total length of mains is 29,409 feet. 

758. Records and Maps.—All constructive features pertaining to the 
distributing system should be carefully recorded on maps of adequate 
size and suitably indexed. The exact location of pipes, hydrants, and 
valves is of special importance. It will be convenient to have two sets 
of maps for this purpose: one on a small scale showing arrangement 
and size of piping and points of connection, and a set of large-scale 
maps, each one showing a comparatively small section of the system, 
on which the detailed information can be recorded. 


LITERATURE. 

1. Freeman. The Arrangement of Hydrants and Water-pipes for Protection 

of a City against Fire. Jour. New Eng. W. W. Assn., 1892, vn. 
pp. 49, 152. 

2. Fanning. Distributing-mains and Fire-service. Proc. Am. W. W. Assn., 

1892, p. 88; Eng. News , 1892, xxvm. p. 42. 

3. Report of the Boston Water Board, 1893, contains extracts of a valuable 

report by Dexter Brackett on fire protection in various large cities. 

4. Brackett. Capacity of Steam Fire-engines, Hydrants, and Hose. Jour. 

New Eng. W. W. Assn., 1895, ix. p. 151. 


* Report of Foster Crowell to the Merchants' Association of New York City on 
Auxiliary Salt-water Supply, 1900. 





LI TER A TU RE. 


7 1 5 

5. Weston. The Separate High-pressure Fire-service System of Providence, 

R. I. Jour. New Eng. W. W. Assn., 1898, xm. p. 85; Eng . 
News, 1898, xxxix. p. 196. 

6. Crowell. Report on an Auxiliary Salt-water Supply for Fire-protection, 

Street-washing, Sewer-cleaning, and Other Purposes. Made to the 
Merchants’ Assn., N. Y. Eng. Record, 1898, xxxvn. p. 124. 

7. The Record System of the Water-works Department, Detroit. Eng . 

Record, 1898, xxxvn. p. 230. 

8. Newcomb. Experiments on Various Types of Hydrants. Trans. Am. 

Soc. M. E., 1899, xx. p. 494. 


CHAPTER XXIX. 


OPERATION AND MAINTENANCE. 

759. Conduits and Pipe-lines. —The maintenance of conduits and 
large pipe-lines involves chiefly the work of cleaning and repairing. 
The various special structures should be frequently inspected to detect 
any sign of weakness, and in the case of large aqueducts the entire 
line should be regularly patrolled. Exposed masonry will need occa¬ 
sional repointing, and at points of excessive wear may need renewal 
at intervals. The right-of-way should be properly taken care of, and 
slopes of earthen embankments kept in good form. Culverts and 
other waterways must be looked after to see that they are not 
obstructed. Air-valves of pipe-lines must be frequently inspected and 
be kept in working order; other valves require less frequent inspection. 
If the water carries sediment and has a low velocity, the pipe-line 
should be occasionally flushed by opening the blow-off valves. Gates 
at terminal points and at intermediate reservoirs require frequent 
adjustment to regulate the flow in accordance with the demand. A 
telephone or telegraph line is almost indispensable in the operation of 
a long conduit. 

Masonry conduits are likely to become coated with slime and 
organic growth, which will cause a large diminution of their carry¬ 
ing capacity, and if allowed to remain may affect the quality of the 
water. In such a case the aqueduct should be cleaned regularly once 
or twice a year, or at longer intervals, depending on the rapidity of 
the accumulations. In cleaning the aqueduct it is emptied and then 
swept with brushes and scrapers, or the work may be done by 
mechanical brooms mounted on cars, as was at one time the practice 
with the Sudbury aqueduct. Experiments made on this aqueduct, and 
also on the new Wachusett aqueduct of Boston, shows that the carry¬ 
ing capacity is in each case reduced about 10 per cent by one year’s 
accumulation of slime. The original capacity is very nearly restored 
by the cleaning which the aqueducts regularly receive. 


716 




CONDUITS AND PIPE-LINES. 


717 

Cleaning and repairing should be done, if possible, at a favorable 
season, so as to render the risk of an interruption in the supply as 
small as may be. In a well-constructed aqueduct or pipe-line the 
expense of repairs should be very slight. 

Large steel and cast-iron pipe-lines will rarely need to be emptied 
for cleaning; but in some cases accumulations of organic growth have 
foimed, which greatly obstructed the flow and which could not be 
removed by blowing off. In such a case the pipe should be cleaned 
in the same way as a masonry structure, or by the use of mechanical 
scrapers as described below. The tuberculation, which occurs to a 
greater or less extent from the corrosion of the iron, often seriously 
reduces the carrying capacity of the pipe. The removal of such 
incrustation will restore a large part of the lost capacity, and may be 
a much more economical method of increasing the pressure in a system 
than by adding new pipes. 

760. Use of Mechanical Scrapers in Cleaning Small Pipes. _A 

method of cleaning cast-iron pipes which has been used extensively in 



Side Elevation. 



Longitudinal Section. 

or . 5 * 10* 15* 20* 25 ”. 

L.J..1 I I 1 L. 1 1 1 1 _1_ I _ I- 

9 - inch Scraoer, ’ 

Fig. 231.—Pipe-scraper. 

(From Engineering News, vol. xliv.) 



Front Elevation. 



Cross Section . 


England, and at a few points in the United States and Canada, is by 
the use of mechanical scrapers propelled by the water-pressure. These 
have been employed chiefly to remove hard incrustation, but a similar 
device can be used for removing less resistant obstructions. The 
general form of such scrapers is shown in Fig. 231, an illustration of 
one recently used at Torquay, England.* It consists of a scraping 


* See paper by Wm. Ingham before Inst. M. E. Abstract, Eng. News, 1900, 
xliv. p. 154. The paper also contains a description of a mechanical brush for 
removing peaty deposits. 
















































































































7i8 


OPERATION AND MAINTENANCE. 


mechanism fastened, by means of a jointed rod, in front of two propelling 
pistons which are rigidly connected together. The scraping-blades 
are held against the pipe by heavy springs. The scraper is introduced 
into the pipe through a long hatch-box, or through an opening made 
by removing a section of pipe. After closing the pipe a blow-off valve 
is opened at a point in advance, and the scraper is pushed along by 
the water. The apparatus may be followed by the noise it makes, and 
this should be done in order to locate it if it should stick. The velocity 
can be regulated by the blow-off valve. At Torquay such an 
apparatus was used as early as 1866 in cleaning an uncoated cast-iron 
pipe. The operation is now carried out at that place every year. 
The scraper here described will pass around a curve of a radius equal 
to about fifteen times the pipe diameter. The cost of cleaning 9- and 
10-inch pipes, at Torquay, was, for labor alone, $3.50 per mile. 

Scrapers similar to the one here described have been used at 
Halifax since 1880, certain mains at that place being cleaned twice a 
year, on account of the necessity of reducing the loss of head to the 
lowest possible limit. In 1898, 1 12,803 feet of mains was cleaned at 
Halifax at an average cost of about 0.4 cent per foot. For some of 
the pipes the cost was as low as 0.3 cent per foot. 

761. Pumping-stations.—Where a water-supply has to be artificially 
elevated, the pumping-station expenses constitute by far the largest 
portion of the operating expenses of the water-works system. It is 
therefore of the greatest importance that the highest efficiency be 
maintained in this part of the service. This can be secured only 
through skillful attendance, and the best results will be obtained by 
paying good wages to good men. The item most susceptible of varia¬ 
tion is the cost of coal, and every effort should be made to reduce this 
to the lowest practicable limit. A daily record should be kept of the 
weight of coal and of ashes, so that the efficiency of the service can be 
known at all times. Frequently a premium paid for low coal con¬ 
sumption is of much aid in this matter. Sufficient reserve boiler and 
pumping capacity must be provided to enable repairs to be made and 
the boiler to be regularly cleaned and overhauled. Reserve machinery 
should be operated frequently to make sure it is in good condition and 
can be started when called for. This is especially important where it 
is depended upon for fire-pressure. Careful attention must be given 
to pump-valves and plunger-packing in order to keep the leakage or 
slip a minimum. Air should not be allowed to get too low in air- 
chambers or to accumulate too much in vacuum-chambers. Suction- 
pipes should be kept air-tight and a free entrance provided at all times 


THE DISTRIBUTING SYSTEM. 


719 


for the water. The motive power, whatever it may be, should be 
maintained at a high efficiency, and should have the same careful 
attention as is given to other high-class machinery. 

Records should, of course, be kept of the amount of water pumped 
per day, and the pressure maintained; also of the time during which 
special fire-pressure is furnished, and the amount of water pumped at 
this pressure. Recording pressure-gauges are of the greatest value in 
maintaining the efficiency of a plant. By the use of several such 
gauges, placed in different parts of the city, a valuable record may be 
obtained of the actual working-pressures under different conditions. 
Such records will be of especial value at times of fires, and, if the pres¬ 
sure is insufficient, will determine whether it be due to low pressure at 
the pumps or to inadequate size of mains. Recording-gauges serve 
also as quick detectors of pipe breakages and the occurrence of 
stoppages, so that means can be at once taken to remedy the trouble. 
Probably no other detail of equal cost is of such great value to the 
superintendent as is a reliable recording-gauge. 

762. Distributing-reservoirs, Stand-pipes, and Tanks.—The main¬ 
tenance of earthen reservoirs calls for little more than has already been 
mentioned (page 321). The cleaning of such reservoirs may need to 
be done frequently. It is usually accomplished by flushing out the mud 
through the waste-pipe by means of a hose, as in the cleaning of 
settling-basins. Stand-pipes and tanks may require occasional flush¬ 
ing or blowing out, and will need to be repainted at intervals of a few 
years. They should also be inspected for signs of excessive corrosion 
or of electrolysis, and for any indication of weakness or wear at the 
base. Wooden tanks need rigid and frequent inspection to ascertain 
the condition of the wood and of the hoops. One or two of the latter 
will probably need to be occasionally removed to determine this point.. 
Details should be inspected for leaks. Any automatic or quick-acting 
valve should have special attention to make certain that it is in working 
condition. 


THE DISTRIBUTING SYSTEM. 

763. In the operation and maintenance of a distributing system 
there are to be considered, besides the questions of construction 
already discussed, the cleaning of pipes, detection of leaks, repairs of 
pipes, prevention of corrosion, provision against electrolysis, thawing 
of frozen pipes, care of valves and hydrants, detection and prevention 
of waste, and the use of meters. 


7 2 ° 


OPERATION AND MAINTENANCE. 


764. Mains and Service-pipes.—A method of removal of incrusta¬ 
tion has already been described in Art. y6o. To remove sediment 
from the pipe system use is made of blow-off valves or hydrants. Dead 
ends may need quite frequent flushing on account of odors and bad 
tastes developing in the stagnant water. Large leaks in mains will 
quickly make themselves known, especially if a recording pressure- 
gauge is in use. Prompt action in shutting off the supply is often 
necessary to prevent heavy damage. Small leaks, if occurring in clay 
soil, will usually be indicated by the appearance of water at the surface, 
but in porous soils, and especially near sewers or drains, quite large 
leaks may go unnoticed for years. These may, however, be detected 
by the method described in Art. 768 for the detection of waste. 
Leaks in services, between the curb-cock and the house, can also be 
likewise detected. Broken sections of pipe must be cut out and 
replaced, either by cutting the pipe and putting in a short piece by 
means of sleeve-joints, or by melting out the lead joints of three sec¬ 
tions and introducing a new length of pipe. 

765. Electrolysis .—A serious form of corrosion which has given 
trouble in many cities is the electrolysis which is caused by return 
currents from single-trolley electric railways. In this system the 
return current is supposed to pass through the rails, but as these are 
not insulated, a portion passes through the earth to neighboring pipes 
or other conductors leading in the right direction. This current then 
flows along the pipe with more or less resistance until it reaches a 
neighborhood where the rails or some other conductors are of lower 
potential than the pipe, this being usually in the vicinity of the power- 
station. The current then leaves the pipe, and in so doing sets up 
corrosive electrolytic action. Such action takes place only where the 
current passes from the pipe to the ground, and not where the current 
passes from the ground to the pipe. It depends in amount upon the 
strength of the current, and upon the character of the salts in the soil. 
If the current in the pipe is strong, corrosion will also take place near 
the joints. This is due to the fact that the joints offer relatively high 
resistance, thus causing a part of the current to leave the pipe and pass 

. around the joint through the soil or the water and back to the pipe on 
the other side. This corrosion near the joint is apt to be much less 
than at other points, but recent reports indicate that it is likely to be 
serious. 

Electrolytic corrosion is in some cases so rapid that pipes are 
practically eaten through in three to four years, and some of the worst 
ceases have occurred where the pressure is but 1^ volts. At Peoria, 



THE DISTRIBUTING SYSTEM. 


72 I 


Ill., a stand-pipe which failed had been badly corroded by electrolysis, 
and this was doubtless a prime cause of its failure. 

The remedies for electrolysis should apparently rest entirely with 
the railway companies. The double trolley is the only complete 
remedy, and it has been applied extensively, and with success, in one 
or two places. A very important aid in preventing electrolysis is the 
construction of a good return conductor by means of good rail-bonding 
and the use of adequate return wires. Then in those districts where 
the pipes are of higher potential than the rails, if good, low-resistance 
connections are made between rails and pipes, or from pipes to special 
return wires, the current will leave the pipes without passing into the 
ground and without causing trouble. Voltmeter tests between pipes 

and rails, at various points over the city, will determine the danger area, 

% 

but such tests should be made under a variety of conditions and at 
occasional intervals. Pipes and rails should not be connected outside 
of the danger area, as this only aggravates the trouble by conducting 
more current into the pipes. This method of making connections to 
the pipes does not obviate the trouble at the joints, but rather in¬ 
creases it, as it adds to the conductivity of the pipes. 

It has been proposed to insulate the pipes by the occasional use of 
a wooden section, or by the use of wooden joints, so as to render the 
pipe a poor conductor. The success of such means would depend upon 
whether the current could be sufficiently reduced to avoid electrolysis 
at the end of each individual section, as now occurs at the joints. 

766. Thawing Frozen Pipes .—Not infrequently considerable trouble 
arises from the freezing of service-pipes which are not placed at a suffi¬ 
cient depth. Occasionally, also, small mains are frozen. Where the 
proper facilities exist the best way to thaw frozen pipes is by warming 
them with an electric current, a method applied for the first time by 
Professors Jackson and Wood at Madison, Wis, in 1898-99, and 
which has been used in many places since then. 

For thawing service-pipes a current of 200 to 300 amperes at a 
pressure of 50 volts is satisfactory, and will ordinarily thaw a pipe in 
from 20 to 30 minutes. The current can conveniently be taken from 
electric-light wires and reduced by a transformer. Connections can 
readily be made to a faucet in the house and to a fire-hydrant outside, 
or to faucets in two houses. To regulate the current large sheet-iron 
terminals can be immersed in a bucket of salt water. Direct connec¬ 
tion to house-lines should not be made on account of the danger of 
fire. A 6-inch main 320 feet long has been thawed in two hours with 
a current of 350 amperes at 100 volts. 


722 


OPERATION AND MAINTENANCE. 


Where the electrical method cannot be used steam may be 
employed, not only to warm the pipe, but to excavate through the 
frozen ground in a way similar to the operation of the water-jet. The 
pipe may thus be reached at points 4 to 5 feet apart and gradually 
thawed out. Service-pipes are often thawed by the use of a small 
steam-pipe inserted in the service-pipe through the house end, or from 
an opening at an excavation outside. Ground may be thawed by 
maintaining a fire on the surface for several hours, or more readily by 
the use of a gas-flame projected against the soil. 

767. Valves and Hydrants. —Valves should be inspected occasionally 
to detect leakage and to ascertain if they are in working order and the 
boxes clean. Fire-hydrants require very careful attention, especially 
in cold climates, as it is of the greatest importance that they be at all 
times available. The chief trouble with fire-hydrants is from the freez¬ 
ing of the valves due to imperfect drainage, although a hydrant branch 
sometimes freezes up 

Hydrants should 

weather and put in good condition. Valves should be tight and the 
hydrant thoroughly drained. If so located that the hydrant cannot be 
drained, it should be pumped out each time after being used. To 
ascertain if a hydrant is drained, a lead weight tied to a graduated cord 
can be let down through a nozzle. Hydrants should never be opened 
unnecessarily in cold weather, and never by others than those responsi¬ 
ble for their condition. In very cold climates it is found desirable after 
using a hydrant to oil the packing and the nut at the top with kero¬ 
sene in order to prevent sticking of the valve and nut. 

To thaw frozen hydrants, a small portable steam-boiler is com¬ 
monly employed, which is provided with a length of hose for conduct¬ 
ing steam to the bottom of the hydrant. Hot water may also be used, 
and for mild cases a little salt may be effective. After thawing, the 
water should always be pumped out. 

768. Detection and Prevention of Waste. —From the data given in 
Chapter II it was made evident that a very large percentage of the 
water supplied to American cities is wasted by the consumer and lost 
by leakage. In many cities the consumption of water is easily double 
the amount which can possibly be made use of, and in a very large 
proportion of them the wastage is fully one-third of the entire quantity 
supplied. This excessive use of water not only increases the cost of 
pumping unnecessarily, but adds to the expense in all parts of a water¬ 
works system. Its effect is noticed perhaps most of all in the reduction 
of pressure, since the frictional head is nearly proportional to the 


be carefully examined on the approach of cold 






DETECTION AND PREVENTION OF WASTE. 723 

square of the discharge. For the same reason a moderate reduction 
of the consumption will result in a large increase of pressure. The 
problem of waste-prevention is thus seen to be one of great economic 
importance. 

Unquestionably the easiest and most rational method of prevent¬ 
ing the waste of water is by the use of meters, so that each consumer 
will pay for what he uses. It furnishes also the most equitable basis 
for charging up the cost of service, as by any other system the careful 
user is forced to pay for the water wasted by his careless neighbor. 
Tlie use of meters is becoming much more general, and in most cities 
the larger consumers, at least, are now metered; but a very large part 
of the loss or waste is due to the small consumer, so that the full 
benefit of the system will not be felt until the use of meters becomes 
general. Usually much opposition is raised to the introduction of 
meters, but after they have been put into use the results are commonly 
such as to cause them to be greatly favored by the community. The 
effect of the use of meters has been generally discussed in Chapter II, 
and many individual cases could be cited showing the great economy 
consequent upon the introduction of the meter system. As a system 
of waste-prevention it is always in service, and for that reason is far 
superior to any system of inspection. In nearly all cases the decrease 
in cost of supplying water after the adoption of meters much more than 
balances the cost of the meters. 

If meters are not used, some method of inspection is highly 
desirable whereby the most serious cases of waste can be detected and 
the consumption kept within reasonable limits. The most common 
method is a house-to-house inspection, carried out one or more times 
per year for the purpose of examining the plumbing fixtures. Any 
leaky or imperfect fixture is ordered repaired, and the premises 
reinspected shortly to make sure that the order has been complied 
with. Persistent refusal is followed by the shutting off of the supply. 
This method of inspection cannot be carried out frequently, and is of 
no value in preventing willful waste through open fixtures. 

A comparatively effective method of house-to-house inspection was 
employed temporarily in St. Louis to avoid a water scarcity. A night 
inspection was first made at the curb-cock by means of a long key with 
the end flattened so that the ear could be held against it. By turning 
the water off and then turning on again, a flow as small as 5 gallons 
per hour could be detected by the hissing noise made. Any appreci¬ 
able flow at night was inquired into next day, the house fixtures 
inspected, and notice given to avoid the waste of water. The same 



724 OPERATION- AND MAINTENANCE. 

house was shortly reinspected, and after two or three notices to repair 
plumbing or stop waste the water would be shut off. 

Next to the use of meters probably the best system of control is 
the use of the Deacon waste-meter system, whereby the rate of con¬ 
sumption in any small section of the distributing system can be 
determined. The Deacon waste-water meter is so constructed as to 
indicate at all times the rate of flow through it, and by suitable 
mechanism the rate is recorded on paper.* In the use of this meter 
the city is divided into sections of a few blocks each, and a by-pass for 
meter-connection is so arranged that by closing valves all the water 
for the district will pass through the meter. In inspecting a district, 
a meter is applied and two or three twenty-four-hour curves obtained. 
If the night consumption is large, thus showing much waste, this waste 
is then localized to certain streets, as far as possible, by shutting off 
different streets in succession and noting the resulting curves. Finally 
the houses in the worst streets are inspected, or the excessive waste 
localized still further by closing off individual services and noting the 
effect on the record, or by the same method as employed at St. Louis. 

This system of inspection was introduced by Mr. G. F. Deacon in 
Liverpool in 1873, and is in general use in many cities in England, 
where it is considered of great value. It has also been used for many 
years in certain districts of Boston, but the cost of the inspection is 
about $100,000 for a population of 350,000, and the system is about 
to be abandoned. + Mr. Freeman estimates that the annual cost of the 
complete meter system for New York City would be about $215,000 
per year, and much less than the Deacon waste-meter system. 

One of the weak points of the meter system is that it fails to detect 
leaks in the mains or in the services beyond the meters. The Deacon 
system is advantageous in this respect, for by shutting off all services 
the leakage in the mains is at once known. It may thus be applied 
to good advantage even where the meter system is in operation, if a 
large amount of water is “unaccounted for.” To localize a leak in 
a main, a waterphone may be used, which consists of a staff of wood 
or iron having at one end a diaphragm and ear-piece similar to a tele- 
phone-receiver. The staff is placed against the pavement over the 
pipe at various points, and the ear applied to the receiver, when any 
sound made by a leak is readily perceived. 

Any method of waste-prevention except by the use of meters is 
of temporary value only and must constantly be repeated, and, to be 

i. - ——————^ , 

* See illustration in Trans. Am. Soc. C. E., xxxiv. p. 199. 
f Freeman, Report on New York’s Water-supply, 1900, p. 77. 





METERS . 725 

effective at all, must be supported by strong laws and good plumbing 
ordinances. 

769. Meters.—Water-meters may be divided into two general 
classes: the positive displacement meter, in which a definite quantity 
of water passes at each complete movement (neglecting the effect of 
the slight clearance necessary), and the inferential meter, in which the 
moving water actuates a screw or other similar mechanism and the 
amount of flow is inferred by the number of revolutions of the screw. 
The former type is in general use in this country, but the latter is a 
common form abroad. Both forms are sufficiently accurate at ordinary 
rates of flow, but the inferential type is the less accurate at low rates. 
Of the displacement meters there are the piston type, having either a 
reciprocating or a rotary piston, and the disk type, in which a disk has 
a sort of wobbling motion in a closed chamber. Most of the meters 
in use are of the rotary-piston or the disk type. Many different kinds 
of meters are on the market, most of which will give satisfactory 
service if properly treated, and many of them have been thoroughly 
tested by years of use. No new form of meter should be adopted 
without thorough and long-continued tests, and in all cases it is well 
to specify the desired requirements of a meter, and to test all new 
meters, in order to insure uniformly good workmanship. 

The general requirements of a meter are: a fair degree of accu¬ 
racy, ability to register approximately quite small rates of flow, suit¬ 
able capacity for a given loss of head, durability, and low cost. All 
of these requirements except that of durability can readily be deter¬ 
mined by a brief test. Some notion of the durability can also be had 
by a careful inspection of the parts, and by running a meter at a rapid 
rate for a considerable period and again determining its accuracy and 
sensitiveness. Maintained accuracy, accessibility, and ease of repairs 
are the most important qualities of a meter. 

Great accuracy in the measurement of water is unnecessary. Most 
meters on the market will register within 1 or 2 per cent of the correct 
amount at ordinary rates of flow, which is abundantly accurate. To 
avoid dissatisfaction it is desirable that the error of registration be in 
favor of the consumer. A small error is otherwise of little conse¬ 
quence. 

Sensitiveness, or accuracy at low rates of flow, is much more 
difficult to secure, and is a point in which meters differ more widely. 
Sensitiveness is desired in order that some account may be taken of 
small leaks, which in the aggregate may amount to a large proportion 
of the total flow. If the consumption of a family be 150 gallons per 


^26 


OPERATION AND MAINTENANCE. 


day, this will be at an average rate of about 6 gallons per hour. A 
flow of water at a uniform rate of one-half this amount would not 
move some meters at all. Great accuracy for small rates is not needed, 
but it is desirable that small flows be accounted for in part at least. A 
sensitiveness of about 90 per cent registration for a flow of 10 gallons 
per hour ought readily to be obtained. 

In a test of fourteen different kinds of meters by J. W. Hill,* 
several of the f-inch meters tested would register a flow of 10 to 12 
gallons per hour with less than 10 per cent of error. Tests of seven 
meters by J. W. Smith + gave a registration of 95 per cent of the flow 
with rates of 3 to 24 gallons per hour. His experiments also showed 
little reduction of accuracy or sensitiveness in the best meters, after 
registering an amount of water corresponding to thirty-five to forty 
years of service, and most were in good condition after a use corre¬ 
sponding to one hundred years of service. In general, the disk meters 
experimented upon showed a more uniform degree of accuracy at 
different rates and a better maintained accuracy than the piston type. 
The figures just mentioned cannot be taken as indicating the actual life 
of a meter, as many other things besides the actual wear affect the 
durability. The actual life of a good meter is probably not over 
twenty years, and in many cases will be less than this. The accuracy 
and durability depend much on whether the water contains suspended 
matter, and upon the character of the same. 

Meters should be so designed that the various parts will be easily 
accessible and readily replaced, and the moving parts protected from 
serious injury by frost. The latter object is usually accomplished by 
frost-bottoms of cast iron, or cast-iron cases, made so as to be more 
easily broken than other and more costly parts of the meter. 

The loss of head in a meter is a matter of some importance, as this 
virtually determines the size necessary for a given capacity, although 
meters are usually rated according to the size of connecting pipes. 
The ordinary sizes for domestic service are -J and f inch. The loss of 
head in seven f-inch meters tested by J. W. Smith, varied from 3 to 
12 pounds for a rate of flow of 10 gallons per minute, a rate which 
would consume about 70 feet of head per 100 feet of f-inch pipe. For 
5 gallons per minute the loss of head ranged from 1 to 3 pounds. 
Mr. Hill found in disk meters, for 10 gallons per minute, a loss of 6 to 
8 pounds, and in piston meters 7 to 13 pounds. For 5 gallons per 
minute the losses were, respectively, 2 to 2f, and 2 to 3 pounds. 


* Trans. Am. Soc. C. E., 1899, XLI. p. 326. 
f Ibid., p. 359. 






FINANCIAL . 


72 7 

The cost of -inch meters is ordinarily from $8 to $12 each; and 
'cost of setting $1.50 to $3.00. The cost of maintenance of meters at 
Providence, R. I., where careful accounts have been kept, is as follows: 
Interest on meters and setting, 50 cents; depreciation, assuming a life 
of twenty years, 75 cents; maintenance and repairs, testing, etc., 46 
cents; reading and computing bills, 42 cents; total, $2.13. The cost 
of repairs at several other places is variously reported at from 10 to 36 
cents per year. 


FINANCIAL. 

770. General Considerations.—The financial management of a muni¬ 
cipal water-works department is a matter of much importance to a 
community, inasmuch as upon this management depends largely the 
question of rates and, to some extent, of other forms of taxation. The 
total cost of the service must eventually be borne by the community, 
but much care is necessary in fixing the rates so that the expense will 
be equitably distributed, both with respect to various individuals at the 
present time, and with respect to future generations. To fix the rates 
equitably requires, first, a careful calculation of the expenses to be met; 
then a determination of how much should be met at the present time 
and what portion should be left to future generations; then what pro¬ 
portion of the total expense should be raised by water rates and what 
portion, if any, by general taxation; and finally, whether it be wise or 
expedient to so adjust the rates that the revenue will exceed the 
expenditure and so act to lower taxation in other ways. In the case 
of private companies the last element would represent the profit. 

In many respects the question is largely a matter of bookkeeping, 
but it is highly desirable that a proper and businesslike method of 
accounting be adopted, both as an aid in equitably fixing the charges, 
and to enable the public to know the exact financial condition of the 
water department as a separate business. 

771. Expenses and Charges to be Met.—The yearly expenses and 
charges will be included under some or all of the following heads: 

1. Interest on bonded debt incurred for construction. 

2. Yearly operating and maintenance expenses. 

3. Yearly payment into a sinking fund for liquidating the bonded 
debt. 

4. Yearly payment into a depreciation fund to provide for the 
renewal of various parts of the works when worn out or otherwise 
rendered valueless. 




728 


OPERATION AND MAINTENANCE . 


5. Yearly cost of extensions and improvements. 

6. Profit. 

Items (1) and (2) must evidently be fully met year by year by the 
annual income, and not by borrowing, if the department is to remain 
solvent. The only question is as to what should be included under 
the term maintenance. In some works it is customary to charge up 
some part of the cost of extensions to maintenance; also the replacing 
of small pipes with larger ones, and renewals of various other portions 
of a plant. But to keep the question clear it is usually considered 
better to include under maintenance only the regular operating 
expenses and the cost of minor repairs. 

(3) and (4). In addition to the interest and maintenance expenses, 
a fund must be provided from the annual income, either for the pay¬ 
ment of the borrowed money by the time the works are worn out, 
or for rebuilding the various parts when necessary; otherwise a city 
would, in the course of time, find itself with a worn-out plant on its 
hands and a bonded debt in addition. To provide both a sinking fund 
and a depreciation fund would be to tax the present generation for the 
entire first cost of the works, and for its renewal or its maintenance in 
perfect condition. This method of management is usually considered 
much too liberal towards the future generations, but may be adopted 
in part where the city finances are in good condition. 

In actual practice the sinking fund usually receives the most and 
often the only consideration, and by some States such a fund must be 
provided for. If the sinking fund be adjusted to pay the bonds at the 
end of a period corresponding to the life of the plant as a whole, or 
for safety a little short of this time, then the sinking-fund provision is 
equivalent to a fund for depreciation, and the finances will be held in 
equilibrium. Renewals will then be paid for by a new issue of bonds, 
and the payments into the sinking fund will continue. To provide for 
contingencies and to relieve the future generations to some extent, it 
is considered good policy to make the sinking fund such as to pay off 
in time all the original debt, including that portion covering the per¬ 
manent parts of the plant. 

If a sinking fund is not provided, then a depreciation fund is neces¬ 
sary. This should be sufficient to furnish funds for the renewal or re¬ 
placement of old parts, and, as a margin of safety in calculating the 
payments into this fund, the more permanent portions of the works 
should be assumed to have a limited life. A portion of the deprecia¬ 
tion fund can then be used to gradually extinguish a part of the bonded 
debt. 


FINANCIAL. 


729 


(5) The cost of extensions may properly be met in the same way 
as the cost of new works, namely, by issuing bonds and at the same 
time providing a corresponding increase in the sinking or the deprecia¬ 
tion fund. Such expenses are, however, as a matter of accounting, 
often paid in part from the annual receipts, or by general or special 
taxation, or by both methods. 

(6) As a general proposition there can be no “ profit ” derived by 
a city from supplying itself with water. If more is paid into the 
treasury than sufficient to meet the expenses, it can only be considered 
as a sort of indirect tax levied for other purposes. 

From these considerations it is evident that the annual charges 
upon the community must on the average cover at least the in¬ 
terest on the bonded debt, the operating expenses, including ordi¬ 
nary repairs, and a payment into a sinking or a depreciation fund. 
(For formulas for calculating sinking or depreciation funds see page 
208.) 

772. Relative Cost of the Different Services Performed by a Water¬ 
works.—The functions performed by a water-works are: (1) to furnish 
water for private use; (2) to furnish water for public use on the streets, 
and for sewers, fountains, public buildings, etc. ; and (3) to furnish fire 
protection to property. In (1) and (2) the cost of service maybe con¬ 
sidered approximately proportional to the quantity of water supplied, 
but in (3) it is out of all proportion to the amount of water used, for 
while the cost of construction is greatly affected, the total amount 
of water consumed is slight. The extra cost involved in furnishing 
adequate fire protection is due to largely increased pumping capacity, 
increased size of mains, reservoirs, or stand-pipes, cost of hydrants, 
and increased cost of maintenance. Estimates of careful observers 
place the proportion of interest, depreciation, and maintenance expenses 
chargeable to fire protection at one-third or one-half the entire cost. 
Another very considerable part of the expense which is not directly 
chargeable to present consumers of water is the provision made for 
future growth. The expense of this in first cost may also easily be 
one-third the entire cost of construction. 

773. Sources of Revenue.—The sources of revenue are the water 
rates and the funds received by general taxation. The former are paid 
by those who use the water, and more or less in proportion to the 
amount used. The latter are paid by assessment on all taxable 
property. If the revenue be so raised that each interest served be 
•charged according to the cost of the service, it would appear from the 


73 ° 


OPERATION AND MAINTENANCE. 


preceding article that the cost of furnishing water to private consumers 
should be paid by water rates; that the cost of supplying water for 
public purposes should be paid by taxation and according to the 
amount of water used; and that the cost of fire protection should also 
be met by taxation, since the individual is benefited by reason of the 
protection afforded to property. The expense of providing for the 
future should also properly be met by the city as a whole, and there¬ 
fore by general taxation. It would therefore seem that ordinarily from 
35 to 40 per cent of the total expense, plus the cost of the water used 
for public purposes, should be met by general taxation, and the 
remainder of the revenue obtained from the water rates. The exact 
proportion of the revenue which should be derived from each source 
depends much upon local conditions, such as size of town, character 
of supply, etc. In many small towns the works are primarily installed 
for fire-protection purposes, in which case nearly all the expense should 
be met by taxation. It is also good policy to begin with fairly low 
water rates, so as to encourage the use of water, but to enable this to 
be done a large proportion of the expense will have to be met for a 
few years by taxation. 

In most water departments the general principle of distributing the 
cost as above outlined is recognized by making payments from the 
general fund into the water department, either yearly or at irregular 
intervals. In but few places, however, is the system fully carried 
out. 

774. Water Rates—The proportion of the revenue to be derived 
from private consumers requires careful consideration in its adjustment. 
The most equitable method of apportioning the cost is by the meter 
system. In fixing rates under this system, allowance should be made 
for the fact that quite a large percentage of the water recorded at the 
pumping-station cannot be accounted for (Chapter II), and rates 
per unit of volume registered by the meters must be correspondingly 
raised. 

Meter rates are usually graduated, that is, a less rate is charged for 
large quantities than for small ones. This is partly on the ground that 
the cost of meter maintenance, keeping of accounts, etc., is propor¬ 
tionally greater for small quantities, and partly by reason of the policy 
of encouraging the operation of factories which contribute largely to 
the general prosperity of the community, and which may require large 
amounts of water. In establishing a graduated schedule, it should be 
so made that the lower rate shall apply only to the additional water 



LI TER A TURK. 


7 3i 


used beyond the limit of the next higher rate. An example .of such a 
schedule is that at Madison, Wis., which reads as follows: 


For the first 

5,000 

cu. ft. per 6 months, 

20 cts. 

per 100 

cu. 

“ “ next 

1 5,000 

44 44 

4 4 

10 

< i 

44 44 

4 4 

4 4 n n 

10,000 

44 44 

4 4 

5 

< < 

44 44 

4 4 

4 4 14 4 4 

30,000 

44 44 

4 4 

3 

< < 

44 44 

4 4 

4 4 4 4 4 4 

30,000 

44 44 

4 4 

2 

4 ( 

44 44 

4 4 

‘ ‘ over 

90,000 

44 44 

4 4 

5 

i ( 

44 44 

4 4 

* 

A minimum 

charge 

of $2.25 per 6 months 

is 

made. 



An objection to the meter system which is often advanced is that 
it discourages the use of sufficient water for sanitary purposes, but this 
is entirely obviated by making a small minimum charge, such as given 
above, which will be enough to allow the use of an abundance of water 
for sanitary purposes, and at the same time will cover the expense of 
meter maintenance. 

Most cities meter the larger consumers, but comparatively few have 
yet introduced the full meter system. In such cases private houses are 
charged mainly by the fixture. Usually a minimum family rate is 
charged for kitchen use, then an additional rate for each bath-tub, 
water-closet, wash-bowl, stable-hose, lawn-hose, etc., with often other 
variations depending upon the number of rooms, number of occupants 
of the house, etc. Little data exists as to the actual amount of water 
used by different fixtures, and the rates are largely arbitrary.* 

LITERATURE. 

GENERAL. 

1. Jamieson. The Internal Corrosion of Cast-iron Pipes. Proc. Inst, 

C. E., 1880, lxv. p. 323. Relates to the use of scrapers. 

2. Keating. On the Removal of Incrustation in Water-mains. Trans. Am, 

Soc, C. E., 1882, xi. p. 127. Describes work done at Halifax. 

3. A Conduit-scrubbing Machine. Eng. News , 1892, xxvii. p. 580, 

Machine used at Boston. 

4. Henderson. The Removal of Corrosion from Water-mains. Proc. Inst. 

C. E., 1893, cxvi. p. 307. 

5. Murdoch. Cleaning a Water-main at St. John, N. B. Jour. New Eng. 

W, W. Assn., 1899, xiii. p. 333; Eng. News , 1899, xlii. p. 45. 

Use of scrapers described, 

6. Ingham. Paper before the Inst. M. E. on the Removal of Incrustation 

from Iron Pipes. Abstract, Eng. Record , 1899, xl. p. 725. 

7. Brackett. Experiments made with the Deacon Waste-water Meter 

System. Jour. Assn. Eng. Soc., 1882, 1. p. 253. 


* For rates of many cities see Manual of Am. W. W., 1897, pp- i-xxxiv. 





73 2 OPERATION AND MAINTENANCE. 

8. Holman. House-to-house Inspection to Prevent Water-waste. Jour. 

Assn. Eng. Soc., 1885, iv. p. 368. 

9. Collins. The Prevention and Detection of Waste of Water. Proc. Inst. 

C. E., 1894, cxvii. p. 147. Relates to the use of the waste-water 
meter. 

10. Water-waste Prevention, or Increased Pumping Capacity. Results of a 

thorough investigation of consumption and waste of water in 
American cities, by H. S. Maddock. Eng. News, 1894, xxxi. p. 55. 

11. Hague. The Value of Pressure-records in Connection with Water-works. 

Proc. Am. W. W. Assn., 1891; Eng. Record , 1891, xxm. p. 345. 

12. Bailey. The Care of Fire-hydrants in Winter. Jour. New Eng. W. W. 

Assn., 1899, xiv. p. 1 16; Eng. Record , 1899, xl. p. 387. 

ELECTROLYSIS. 

1. Jackson. The Corrosion of Iron Pipes by the Action of Electric Railway 

Currents. Jour. Assn. Eng. Soc., 1894, xiii. p. 509. 

2. Farnham. Electrolysis of Water and other Subterranean Pipes by Electric 

Currents. Trans. Am. Inst. E. E., April, 1894; Elec. Eng., April 
25, 1894. 

3. Barrett. Report to Commissioners of Electric Subways of Brooklyn on 

the Subject of Electrolysis. Abstract, Eng. Record, 1895, xxxi. 
p. 225. 

4. Electrolysis of Water-pipes at Dayton, 0 . Report of investigation. 

Abstract, Eng. News, 1898, xl. p. 218. 

5. Electrolysis at Kansas City. Report of Prof. L. I. Blake in regard to. 

Eng. Record, 1899, xL.p. 239. 

6. Maury. Electrolysis of Underground Metal Structures. Corrosion of 

the Peoria Stand-pipe and Water-mains. Proc. Am. W. W. Assn., 
1900; Eng. News, 1900, xliv. p. 38. 

METERS. 

1. Rice. The Methods and Apparatus used in the Recent Test of Water- 

meters at Boston. Jour. Assn. Eng. Soc., 1888, vn. p. 285. 

2. Thompson. A Memoir on Water-meters. Trans. Am. Soc. C. E., 

1891, xxv. p. 40. 

3. Gill. The Sale of Water by Meter in Berlin. Proc. Inst. C. E., 1892, 

evil. p. 203. 

4. Thompson. Uniformity of Methods in Testing Water-meters. Jour. New 

Eng. W. W. Assn., 1895, x. p. 77. 

5. Bericht der Commission fur Wassermesser-Normalien. Jour. f. Gasbel. 

u. Wasservers., 1896, xxxix. p. 699. Results of tests on a large 
number of meters, and suggested standards. 

6. Meter-testing Apparatus, Somerville, Mass. Eng. Record, 1898, xxxvm. 

p 402 

7. Hill. The Accuracy and Durability of Water-meters. Trans. Am. Soc. 

C. E., 1899, xli. p. 326. 

8. Nuebling. A Meter-testing Apparatus used at Reading, Pa. Eng. 

Record, 1899, xl. p. 698. 


LITER A TURE . 


733 


FINANCIAL. 

1. Tubbs. Particulars in which Municipal Officers should Protect the 

Municipal Corporations in Granting Water-works Franchises to 
Private Companies. Proc. Am. W. W. Assn., 1892; Eng. News, 
1892, xxvii. p. 518. 

2. The Regulation of Private Water-rates. Eng. News, 1892, xxvii . p. 201. 

3. Coffin. The Financial Management of Water-works. Jour. New Eng. 

W. W. Assn., 1896, xi. p. 63. 

4. Kiersted. Valuation of Water-works Property. Trans. Am. Soc. C. E., 

1897, xxxviii. p. 115. Extensive discussion. 

5. Kuichling. The Financial Management of Water-works. Trans. Am. 

Soc. C. E., 1897, xxxviii. p. 1. 

6 . Manual of American Water-works, 1897. Contains much information 

on the questions of ownership and of water-wates. 

7. Hermann. Water-rates. Elaborate paper before the Am. Soc. Muni¬ 

cipal Improvement. Eng. Record, 1899, xl. p. 459. 

S. Hill. Valuation Clauses in Water-works Franchises. Proc. Am. W. W. 
Assn., 1899, p. 233; Eng. Record, 1899, XXXIX - P- 594 - 





INDEX. 


Aeration: 

effect of, on bacteria, 155 
efficiency, 480 
in removal of iron, 486 
methods of, 479 

Air-chambers for pumps, 612, 677 
for wells, 292 
lift pump, 608 
valves, 560 

Algae, development in reservoirs, 170 
odors due to, 159 
Amoeba coli , 190 
Ammonia, albuminoid, 120 
free, 120 

Anabcena , 159, 160 
Anaerobic cultures, 128 
Analysis of water, sanitary, no 
Analytical methods, different, II2 
value of, 112 

samples, collection of, 108 
bacterial, 109 
chemical, 109 
Anchor-ice, 259 
Anderson process, 487 
Animal tests in water analysis, 129 
Anthrax, vitality of, in water, 194 
fever, 189 

Aqueduct bridges, see Bridges. 
Aqueducts, ancient, 2 
cleaning, 716 
maintenance, 716 
masonry, see Masonry aqueducts. 
Roman, 2 
Zempola, 8 
See also Conduits. 

Artesian strata, capacity of, 100 
Dakota sandstone, 103 
occurrence along the Atlantic Coast, 
102 

occurrence in the United States, 102 
Potsdam sandstone, 101, 104 
value of, 100 

water, bacterial content of, at Du¬ 
buque, 168 
defined, 99 

wells, arrangement of, 300 


Artesian wells, boring of, 296 
in rock, 297 
in soft materials, 296 
casing, 298 

conditions requisite, 98 

cost, 299 

Dakota, 277 

examples, 277, 301 

failure of, 303 

flow of water into, 273 

location, 102 

operation, 301 

predictions concerning, 102 

Rockford, 302 

size, 300 

spacing, 300 

yield, 303 

Asphalt for reservoir lining, 642 
for pipe coating, 515 
Asterionella , 159, 160, 170 
Atmosphere, pressure of, 214 

Bacillus cloaca , 130 

coli communis , as index of fecal pollu¬ 
tion, 130 

methods of isolation, 131 
enteritidis sporogenes , 129, 130 
lactis aerogenes y 130 
typhosus, methods of isolation, 133 
relation of, to colon organism, 131 
Bacteria, effect of sunlight on, 153 
growth of, in spring-waters, 164 
in ice, 160 
in soil, 144 

multiplication of,in water samples, 125 
organic nutriment on growth of, 168 
significance of liquefying, 127 
vitality of disease, 191 
Bacterial analysis of waters, 112, 113 
quantitative, 124 
content of Isar River, 148 
Lake Superior, 156 
Potomac River, 148 
rain-water, 145 
spring-water, 164 
streams, 148 


735 





736 


INDEX. 


Bacterial content of wells, 166, 168 
purification of rivers, 149 
Danube, 149 
Hudson, 150 
Illinois, 151 
Isar, 150 
Rhine, 149 
tests of filters, 461 
scope of, 123 
Backfilling, 713 
Balanced valves, 562 
Bell-and-spigot joint, 503 
Belting, efficiency of, 590 
Berkefeld filter, 489 

Blood-heat, effect of, on bacterial 
growth, 125 
Blow-off valves, 561 
Boiler-scale, 143, 397, 481 
Bridge, aqueduct, 3, 5, 544 
for pipe-lines, 519, 564 

Canals, cost of, 570 
cross-sections, 536 
details, 537 
flow of water in, 535 
gates, 538 
slopes, 535 
use of, 535 
velocities in, 535 

Carbolic acid and sulphuric acid, effect 
of mixing, 134 

Cast iron, strength of, 501, 597 
Cast-iron pipe: 
branches, 506 

calculations of, 228, 232, 700, 708 

coating, 509 

corrosion, 510, 720 

cost, 550, 571, 572 

covering, 556, 712 

derrick for, 554 

distortion of, 500 

durability, 510 

economical size, 549 

flow of water in, 228 

inspection of, 509 

intakes, 569 

joints, 503 

bell-and-spigot, 503 
flanged, 506 
flexible, 567, 569 
rubber, 506 
sleeve, 506 
special, 569 
standard, 504, 505 
turned, 505 
laying, 553 
manufacture, 507 
material for, 507 
specials, 506 
standard weights, 503 
stresses in, 497 
testing, 510 
thickness, 501 
tuberculation, 510 


Cast-iron pipe, use of, 501 
weight of, 501, 510 
Cement pipe, 527 
Centrifugal pumps, 302, 607, 616 
Check-valves, 562 

Chemical analysis of water, 112, 117 
data, expression of, 117 
interpretation of, 118 
reaction of water, 117 
Chemicals, use of, in detecting pollution, 
hi 

in water purification, 492 
Chlorinated lime in water purification 
493 

Chlorine, increase of, in inhabited areas, 

120 

relation of, to quality, 119 
Cholera, 176 
infantum, 189 
organism, isolation of, 133 
vitality of, in waters, 194 
outbreaks : 

epidemics in the United States, 187 
Hamburg, 188 
London, 187 

Circulation, vertical, of lake waters, 157 
Cities, growth of, 33 
Clark process, 483 
Clear-water reservoir for filters, 456 
for settling-basins, 416 
Closterium , 160 

Coagulants, action of various,411,470,487 
amount required, 409 
efficiency of, 410 
iron, 411, 487 
sulphate of alumina, 408 
use of, in filtration, 460 
in sedimentation, 408 
Colon bacillus, relation of, to typhoid or¬ 
ganism, 131 
significance of, 130 
Color of water, 114 

Comparison of waters by qualitative bac¬ 
terial analyses, 128 

by quantitative bacterial analyses, 123 
Concentration of bacteria in water an¬ 
alysis, 129 

Condensers, value of, 586 
Conduits, canal, see Canals, 
capacity, 533 

cast-iron, see Cast-iron pipe. 

classes of, 532 

location, 533 

maintenance, 716 

masonry, see Masonry aqueducts. 

pipe, see Pipe-lines. 

single vs. double, 533 

steel, see Pipe-lines. 

Consumption of water, by ancients, 8 
effect of meters on, 18, 25 
fire rate, 20, 30, 685 
for commercial purposes, 18 
domestic purposes, 17 
public purposes, 19 




INDEX. 


737 


Consumption for street-sprinkling, 20 
in American cities, 23 
in European cities, 32 
increase in, 17, 24 
influences affecting, 16 
loss and waste, 20, 722 
maximum rate, 31, 685, 691 
total, per capita, 22 
variations in, 26 
daily, 27 
hourly, 28 
monthly, 26 
waste, 20, 768 
Core-walls, 327, 330 
masonry, 331 
position of, 333 
puddle, 330 
steel, 333 
wooden, 333, 339 
Corrosion of pipes, 510, 516, 720 
Coupling-shoes for stave-pipe, 525 
Covered reservoirs, 646 
data on, 648 
masonry, 647 
wooden, 647 
Crenothrix , 128, 162,171 
Croton aqueduct, coefficients for, 248 
sections of, 542 
Crops, use of water by, 59 
Culverts for aqueducts, 544 

Dakota sandstone, 103 
Dams, considered as porous, 323 
earthen, 325 

advantages of, 325 
clay in, 329 

conditions requisite for, 325 
construction, 336 
floods during, 352 
foundation, 336 
hydraulic, 337 
core-walls, 327, 330 
masonry, 331 
position of, 333 
puddle, 330 
steel, 333 
wooden, 333, 339 
cost, 353 
culverts in, 341 
faces, 338 
forms of, 326 
foundations, 326, 335, 338 
gate-chambei s, 343, 349 
screens. 347 
sluice-gates, 348 
height of, 334 
hydraulic construction, 337 
material for, 329 
outlet pipes and valves, 339, 348 
pipes in, 340 
porous, 338 
puddle for, 330 
slopes, 334. 338 
stability, 327 


Dams, earthen, top width, 335 
tunnels in, 341 
wasteways for, 351 
kinds of, 323 
loose rock, 394 
maintenance, 321 
masonry, 356 
advantages, 356 
conditions requisite, 356 
construction, 373, 375 
cost, 387 
curved, 370 
action of, 370 
examples, 372 
draw-off arrangements, 378 
errors in theory, 358, 366 
earth backing for, 377 
examples, 384 
forces acting, 356, 369 
foundation, 373 
earth, 374 
water in, 375 
gate-chambers, 379 
height above water, 370 
high, 363 

examples, 385 
ice action on, 369 
imperviousness, 377 
internal pressure in, 369 
leakage, 377 
low, 361 

examples. 384 
outlet-pipes, 378 
pressures allowable, 361 
profiles, 367, 368 
stability, 359 

high dams, 363, 369 
low dams, 361 
standard profile, 367 
stresses in, 357 
top width, 370 
triangular profile, 368 
valves for, 379 
water-pressure in, 369 
waste-weirs, forms of, 380 
examples, 381, 382, 383 
wave-action on, 369 
Wegmann’s formulas, 364 
weight of, 361 
wind-pressure on, 369 
porosity of, 323 
pressure of water in, 323, 369 
requisites of, 323 
rock-fill, 394 
steel, 392, 393 
timber, 390 
Darcy’s formula, 230 

Data necessary in water examination, 107 
Deacon waste-water meter system, 722 
Death-rates from typhoid, large cities in 
the U. S., 178 
Massachusetts, 178 
Deep-well pumps, 302, 606, 614 
Deep wells, see Artesian wells. 





738 


INDEX . 


Depreciation, calculation of, 209 
of works, 210 
fund for, 728 

Derrick for pipe-laying, 554 
Dilution, effect of, on purification of 
streams, 152 

Direct pumping system, 201 
Disease bacteria, in lake-mud, 158 
vitality of, in water, 191 
disseminated by water, 175 
Disinfection of wells and pipes, 134 
Distillation, 491 

Distributing pipes, arrangement of, 688, 
702 

calculation, 700, 708 
covering, 712 

flow through compound pipes, 698 

location, 710 

loss of head in, 232, 696 

maintenance, 716 

relative capacity, 698 

thawing, 721 

reservoirs, automatic valve for, 661 
capacity, 634 
construction, 640 
cost, 651 
covered, 646 
depth, 639 
elevation, 638 
form, 638 

gate-chambers, 645 
high-water alarm, 662 
kinds of, 334 
linings, 641 
location, 637 
masonry, 644 
maintenance, 719 
outlet pipes, 645 
purpose of, 633 
value of, 633, 637 
valves for, 645 
system, 682 
ancient, 7 

arrangement, 688, 702 
calculation, 698, 700 
cost, 571 

examples, 690, 705 
fire-pressure required, 683 
fire-stieams required, 685 
hydrant location, 687 
maps of, 714 

pressure required, 683, 709 
records, 714 
requirements, 682, 691 
services, 712 
valves, 710 
velocities in, 692 
zones of pressure, 709 
Distribution, effect of, on quality, 169, 
171 

Domestic filters, 489 

Driven wells, see Wells, tubular. 

Dug vs. driven wells, pollution of, 134 
Dysentery, 190 


Earth, pressure of, on pipes, 499 
Earthen dams, see Dams, earthen. 
Efficiency of generators and motors, 583 
Electrical purification processes, 411,486 
transmission, 595 
Electrolysis, 720 
Elevated tanks, see Tanks. 
Embankments, construction of, 336, 640 
for aqueducts, 543 
Energy, equivalent units of, 580 
generation of, 583 
losses, 581, 620 
sources of, 581 
transmission of, 590 
Enrichment cultures, 129 
Evaporation. 52 

from land-surfaces, 55 

determined from stream-flow, 61 
effect of vegetation, 59 
experiments on, 60, 62 
formula for, 61 
from water-surfaces, 53 
at Boston, 53 
Lee Bridge, 55 
Rochester, 54 

calculated, for U. S., 55, 56 
experiments on, 53, 54 
relation to stream-flow, 52 
Examination of water-supplies, 107 
Expansion-joints, 556 

Fecal bacteria, character of, 128 
Fermentation-tube, use of, 127 
Filter, Fischer system, 479 
control, bacterial, 135 
cribs, 307 
galleries, 304 
Filters, domestic, 489 
mechanical: 
action of, 469 
advantages, 473, 477 
arrangement of, 468, 473 
capacity, in U. S., 421 
Continental, 470 
cost, 477 

experiments on, 471 
Jewell, 469 
types, 468 
use of, 471 
value of, 473, 477 
sand, acreage of, 421 

Albany, 435, 438, 448, 454 
arrangement, 421, 431, 444 
beds, size and number, 434 
bacterial control of operation, 461 
capacity, 421, 434 
cleaning, 456 
clear-water reservoir, 456 
construction, 421, 431, 436, 444 
cost, 462, 463 
covers, 438, 439, 647, 648 
depth of, 438 
of water on, 445 
drainage systems, 445 






INDEX. 


7 39 


Filters, sand, drains, loss of head in, 447, 
449 

effluent, bacteria in, 427 
friction in, 450 
drains, 447 
gravel, 449 
sand,443 

gravel, loss of head in, 449 
inlet pipe, 451 
interior of, 438 
intermittent, 464 
loss of head in, 443, 447, 449, 450 
operation, 461 
cost of, 463 
outlet pipes, 451 
period of service, 457 
pipes for, 451, 455 
pure-water reservoir, 456 
regulators, 451 
automatic, 454 
sand for, 441 
analysis, 441 
selection, 442 
washing, 458 
sand bed, friction in, 443 
thickness, 444 
, sand washers, 458 
sediment layer, 425 
scraping, 456 
use of, in U. S., 421 
valves, regulating, 451* 454, 455 
washing of sand, 458 
Zurich, 448 

Filtration, extent of, in soil to effect pu¬ 
rification, 163 
history, 10 
mechanical, 468 

coagulation and, 409, 469 
efficiency, 476 

Experiments, Cincinnati, 472 
East Providence, 474 
Lorain, 474 
Louisville, 471 
Marinette, 475 
Pittsburg, 473 
Providence, 471 
Washington, 474 
sedimentation and, 472 
theory, 469 

sand, bacteria in effluent, 427 
bacterial control, 461 
biological action, 424 
chemical action, 424 
coagulation and, 460 
double, 464 
efficiency, 422, 428 
bacterial, 422. 429 
chemical, 423 

death-rates as measure of, 430 
effect of cold, 440 
rate, 432 
scraping, 457 
effluent, bacteria in, 427 
history of, 420 


Filtration, sand, intermittent, 463 
mechanical action, 423 
rate of, 426, 431, 443 
regulation of, 451 
results of, 422 
sedimentation and, 458 
theory, 423 

through river-bed, 304 
Financial management, 727 
Fire-boats, 713 
Fire-cisterns, 687 
Fire-pressures, 683 
Fire-streams, hydraulics of, 240 
number required, 686 
Fire-supply, cost of, 729 
separate, 205, 713 

Fires, consumption of water for, 30 
Fish-screens, 347 
Fishy odors, 159 
Flexible joints, 567, 568, 569 
Floods, estimating, 70 
examples, 73 
Flow of streams, 64 

annual and seasonal, 74 
estimates, 79, 81 
minimum, 76 
statistics of, 75 

distribution of, through the year, 82 
effect of lakes and ponds, 81 
maximum, 67 

diagrams for, 71, 72 
estimates, 70 
examples of floods, 73 
formulas, 69 
statistics, 68 

methods of estimating, 64 
minimum, 66 
monthly, 78 
units of measure, 65 
Flow of water in filter-drains, 447, 449 
in hose, 241 
in hydrants, 242 
in open channels, 246 
coefficients, 247, 546 
formulas, 246 
Kutter’s formula, 246 
coefficients for, 247 
measurement of, 248 
tunnels, 546 
in pipes, 225 

coefficients for cast-iron pipe, 228 
compound pipes, 698 
Darcy’s formula, 230 
diagram for cast-iron pipe, 232 
distributing pipes, 232, 696 
fire-hose, 240 
Flamant’s formula, 230 
formulas, 227, 231 
friction of water, nature of, 227 
general relations, 225 
Lampe’s formula, 230 
loss of head at entrance, 239 
due to bends, 239 
contraction, 239 




740 


INDEX. 


Flow of water in pipes: 

loss of head due enlargement, 239 
in valves, 239 
Measurement of, 238 
old pipe, 232 
riveted pipe, 235 
service-pipes, 234 
smooth pipe, 235 
wooden pipe, 237 
over weirs, 218 
sharp-crested, 218 
submerged, 221 
various forms, 221 
through filters, 443, 447 
gravel, 92, 449 
nozzles, 241 
orifices, 216 
rock strata, 101 
sand, 91, 443 
Flowing waters, 146 

physical appearance, 147 
Flumes, 538 

Fluorescein, use of in detecting pollu¬ 
tion, hi 

Food-supply, lack of, on bacterial purifi¬ 
cation of streams, 154 
Fountains, water for, 20 
Friction, fluid, 227 
Frontinus, 7 

Fuels, calorific value of, 583 

Galleries, see Filter-galleries. 

Galvanized iron pipe, 528 
Gas-engines, efficiency of, 589 
Gastro-intestinal diseases, 190 
Gate-chambers, 343, 349, 379 
Gates, aqueduct, 545 
canal, 538 

Gearing, efficiency of, 583 
Generators, efficiency of, 583 
Germ theory of disease, 173 
Grassy odors, 159 

Gravel, flow of water through, 92, 449 
Ground-water, 84 

collecting works, 264 
flow of, 91 

Thiem’s method of estimating, 93 
methods of estimating, 89, 90, 93 
form of surface, 85 
formations favorable for, 86, 88 
level of, 85 
occurrence, 84, 88 
quantity available, 94 
Growth of cities, 33 

Hard waters, effect of, on soap, 143 
relation of, to disease, 142 
Hardness of water, 143, 481 
Heat-engines, efficiency of, 589 
High and low service, 709 
High-water alarm for stand-pipes, etc., 
662 

Household filters, 489 
Hydrants, 710 


Hydrants, drainage of, 710, 722 
forms, 711 
freezing, 712, 722 
friction in, 242, 710 
location, 687 
maintenance, 722 
setting, 712 
valves, 711 

Hydraulic dam construction, 337 
grade, 547, 548 
ram, 608 

transmission, efficiency of, 595 

Ice, action of on stand-pipes, 656 
anchor, 259 
bacteria in, 160 
pressure on dams, 369 
Impounded waters, 156 
Impounding reservoirs, see Reservoirs, 
storage. 

Impurities, absorption of, by meteoric 
waters, 145 

Income of water departments, 729 
Incubation at blood-heat, effect of, on 
bacterial growth, 125 
Indol test in water analysis, 128 
Infection of well-waters, 167 
Intakes, 249 
lake, 256 

anchor-ice in, 259 
Chicago, 261 

construction, 258, 568, 569 
cribs for, 259 
examples, 261, 568 
location, 256 
Milwaukee, 260, 568 
sewage pollution at, 256 
submerged pipe, 258, 568, 569 
tunnels, 258 

river, 249 ♦ 

Cincinnati, 255 
construction, 250 
examples, 251, 253, 254 
for gravity supplies, 256 
location, 249 
St. Louis, 254 
Steubenville, 253 
Iron in waters, 142, 161 

amount necessary to impart taste,142 
cause of, 484 
removal of, 484, 485 
use of in purification, 411, 487 
bacterium, 162 
Isochlors, 119 

Joints for pipes, cast-iron, 503 
riveted. 513, 657 
steel, 513, 515 
wood, 521, 522 

Kutter’s formula, 246 

Lactose agar in water analysis, 127 
Lakes, intakes for, 256 




INDEX . 


741 


Lakes, vertical circulation, 157 
Lead, action of waters on, 142, 528 
pipe, 528 

use of by ancients, 2 
Leakage of pipes, 21, 720 
Levee section, 339 

Liquefying bacteria, significance of, 127 
Lithium, use of, in detecting pollution, 
112 

Locking-bar joint, 515 
London, water-supply of, 8 
Loss on ignition, 119 

Low temperatures, influence of, on ty¬ 
phoid, 193 

Mains, leakage from, 21 
Maintenance : 
conduits, 716 
cost of, 728 

distributing system, 720 
pipe-lines, 717 
pumping-stations, 718 
reservoirs, 321 
Malaria, 191 
Manholes in pipes, 557 
in tanks, 663 
Maps, 714 

Masonry, cost of, 387, 570 
weight of, 361 
aqueducts, 539 
construction, 543 
cost, 570 

cross-sections, 540 
Croton, 542 
details, 544 
embankments for, 543 
gates, 545 
maintenance, 716 
materials for, 540 
stability, 540 
Wachusett, 542 
dams, see Dams, masonry, 
reservoirs, 644, 651 
cost of, 651, 652 
covers for, 647 
Melos ini , 159 
Meteoric waters, 145 
Meter rates, 730 
Meters, 725 

accuracy, 21, 726 
cost, 727 
durability, 726 
requirements, 725 

value of, in waste prevention, 24, 723 
Microscopical analysis of water, 112, 114, 
136 

Molding of pipes, 508 
Motors, efficiency of, 583 
Mud, bacteria in, 158, 406 
Multiplication of bacteria in water sam¬ 
ples, 125 

Nitrates, significance of, 122 
Nitrites, significance of, 122 


Odors in water, 116, 159 
due to algae, 159 
fishy, 159 
grassy, 159 

Operation of water-works, cost of, 727 
Organic matter, 120 
Orifices, flow through, 216 
Overturning of lake-waters, 157 
Oxygen consumption, 121 
Ozone in water purification, 492 

Parasitic worms, dangers of, 136 
Paris, water-supply of, 8, 9 
Pasteur filter, 489 

Pathogenic bacteria, detection of, 132 
relation of, to water analysis, 130 
Pediastrum, 160 
Percolation, 52, 55 

determined by stream-flow, 62 
effect of, on quality, i6x 
effect of vegetation on, 59 
experiments on, 60, 62 
relation to stream-flow, 52 
Permanent hardness, 143, 481 
Peroxide of hydrogen in water purifica¬ 
tion, 493 

Physical analysis of water, 112, 114 
Physiological bacterial tests, 127 
Pipe-lines, 532, 547 
bridges for, 564 
calculations of, 549 
construction, 552 
cost, 550, 570 
covering, 556, 754 
crossings, 564 
design of, 547 
details, 556 
economical size, 549 
expansion-joints, 556 
foundations, 553 
freezing, 556 
inspection, 555 
manholes, 557 
material for, 547 
pressures in, 548 
pressure-regulators, 562 
profile, 547 
Rochester, 549 
safety-valves, 563 
terminals, 563 
testing. 555 
valves, 558 
velocities in, 552 
molds, 508 
moss, 172 
scraper, 717 

Pipes, cast-iron, see Cast-iron pipe, 
cement, see Cement pipe, 
corrosion of, by electrolysis, 720 
depth of covering, 712 
freezing, 556, 565 
lead, see Lead pipe, 
leakage from, 21 
location, 711 





742 


INDEX . 


Pipes, maintenance, 717 
materials for, 497 
pressure of earth filling, 499 
water, 497, 548 
protection of exposed, 565 
scraping, 717 
service, see Service-pipes, 
steel, see Steel pipes, 
stresses in, 497 
thawing, 721 
water-hammer in, 498 
wooden, see Wooden pipe, 
wrought iron, 511 

Platinum-cobalt color standard, 115 
wire method of determining turbidity, 
115 

Pneumatic transmission, 595 
Poisonous metals in waters, 142 
Pollution, detection of, by addition of 
chemicals, ill 
Population, estimates of, 33 
Porosity of soils, 86 
Potableness, 142 
Potsdam sandstone, 101, 104 
Power equivalents, 579, 580 
pumps, 599, 605, 606, 607 
efficiency of, 620 
Precipitation, see Rainfall. 

Pressure in distributing system, 683 
of atmosphere, 214 
of water, 214 
equivalents, 579 
gauges, value of, 719 
regulators, 562 
relief-valves, 563 
Prime movers, efficiency of, 583 
Protection of pipes from frost, 565, 676 
Puddle, 329, 330 

Pumping, effect of, on bacterial content 
of well-waters, 167 
work done in, 577 
machinery, arrangement of, 614, 623 
calculation of efficiency, 620 
capacity, 626 
duty, 616, 618 

economy of different designs, 627 
efficiency, 616, 618, 6»o 
stations, design of, 623 
operation of, 718 
Pumps, air-chambers for, 612 
air-displacement, 606 
air-lift, 608 
Allis, 604 

bucket, 609 * 

centrifugal, 302, 607, 616 
classification, 595 
Connersville rotary, 605 
continuous-flow, 606 
deep-well, 606 
details, 609 
duplex, 600 
efficiency, 618, 620 
Gaskill, 603 
Heisler, 602 


Pumps, hydraulic, 605 
hydraulic ram, 608 
impeller, 606 
impulse, 608 
jet, 608 

location of, 614 
power, 599, 605 
reciprocating, 596 
rotary, 605 
slip of, 16, 21 
steam, 599 

steam-displacement, 606 
suction-pipes, 612 
types of, 597, 598 
U pump, 596 
valves, 609 
vacuum chamber, 612 
Worthington, 600, 601 

Purification of streams, 149 
causes, 151 
effect of aeration, 155 

competing organisms, 154 
dilution, 152 
lack of food, 154 
sedimentation, 152 
sunlight, 153 

of water, general statement, 397 
aeration, see Aeration. 

Anderson’s process, 487 
chemical processes, 492 
chlorinated lime, 493 
peroxide of hydrogen, 493 
ozone, 492 
distillation, 491 
electrolytic methods, 486 
filtration, see Filtration, 
for domestic purposes, 397 
for manufacturing purposes, 397 
imperfect, Lausen typhoid outbreak 
due to, 164 
in the soil, 162 
iron-removal, 484 
methods, 398 
objects of. 398 

sedimentation, see Sedimentation, 
softening, 481 
sterilization, 491 

Quality of water, from various sources, 

36 

in ancient times, 8 
relation of, to character, 141 
requirements, 142 

Quantitative bacterial examination, 124 

Rain-water, bacterial content of, 145 

Rainfall, 39 
annual in U. S., 41 
maximum rates, 47 
measurement of, 39 
minimum, 45 
monthly, 44 
statistics, 41 
variations in, 41 




INDEX. 


7 43 


Rain-gauges, 39 
Rain-storms, frequency, 48 
maximum, 48, 49 
Rates, water, 730 
Reservoir dams, see Dams, 
linings, 641 

sediment, bacteria in, 406 
Reservoirs, ancient, 2 

distributing, see Distributing reser¬ 
voirs. 

for pipe-lines, 548, 563 
storage, 311 

capacity, 313, 315, 316 
cleaning of site, 320 
construction, 317 
depth, 319 
location, 317 
maintenance, 321 
organic matter in, 32 
shallow flowage, 321 
surveys for, 318 
Revenue, sources of, 729 
Rivers, intakes for, 249 
Riveted joints, for pipes, 513 
for stand-pipes, 657 
pipes, friction in, 235, 236 
Rocks, porosity of, 86, 101 
Rope-gearing, efficiency of, 590 
Rotary pumps, 605 
Run-off, see Flow of streams. 

Running water, physical appearance of, 
147 

Safety-valves, 563 

Salt, use of, in detecting pollution, 112 
Samples for analysis, collection of, 108 
Sand, analysis of, 441 
effective size, 441 
flow of water in, 91 
washing, 458 

Sanitary survey, value of, 137 
water analysis, nature of, no 
Saprol, use of, in detecting pollution, 
in 

Scale, boiler, 143 
Scenedesmus , 160 
Scrapers, pipe, 717 
Screens, reservoir, 347 
Sediment, bacteria in, 158, 406 
in streams, 147 

relation to bacterial content of rivers, 
148 

Sedimentation, 401 

action of finely divided matter, 407 
sulfate of alumina, 408 
various chemicals, 411 
efficiency, 404 
limitations of, 402 
methods, 402 

of bacteria in purification of streams, 

152 

plain, 403 

theory of, 403 

time required, 403, 409 


Sedimentation with coagulant, 408 
action of chemicals, 411 
amount of chemical required, 409 
efficiency, 410 
time required, 409 
mechanical filtration, 472 
sand filtration, 458 
Self-purification of rivers, 149 
Separate systems of supply, 205, 709, 713 
Service-connections, 712 
Service-pipes, friction in, 234 
maintenance, 720 
materials for, 528 
thawing, 721 
Settling basins, 412 
Albany, 418, 437 
clear-water reservoir for, 416 
drain-pipes, 416 

draw-off arrangements, 414, 415 
examples, 416, 418 
floating-tube for, 646 
form of, 413 

inlet- and outlet-pipes, 414 
methods of operation, 412 
number, 413 
St. Joseph, 418 
St Louis, 416 
size, 413 

Sewage bacteria, B. enteritidis sporog. t 
diagnosis of, 129 
physiological character of, 128 
pollution, value of certain bacteria in, 
130 

Sewer-gas, relation of, to typhoid fever, 
177 . 

Shafting, efficiency of, 590 
Shoes for stave-pipe, 525 
Sinking fund, 209, 728 
Sluice-gates, 348 

Soft water vs. hard in Glasgow, 143 
Softening of water, 481 

Archbutt-Deeley process, 484 
chemistry of, 482 
Clark process, 483 
efficiency, 484 
for boiler use, 484 
Southampton, Eng., 483 
Soil, purification of water in, 16a 
Soils, porosity of, 86 
Solids, total, 118 
volatile, 119 

Sources of water-supply, 36 
Specials for cast-iron pipe, 506 
steel pipe, 515 
wooden pipe, 525 

Species, significance of bacterial, 126 
Springs, 94 
artesian, 96 
bacteria in, 164 
classification 94 
collecting works for, 264 
yield of, 97, 267 
Stand-pipe system, 201 
Stand-pipes, anchorage, 659 





744 


INDEX. 


Stand-pipes, automatic valves for, 662 
bottom details, 659 
capacity, 634 
details, 653 
dimensions, 653 
encased, 663 
foundations, 659 
high-water alarm, 662 
ice-acticn on, 656 
inlet-pipes, 660 
location, 653 
maintenance, 719 
manhole, 663 
material for, 656 
ornamentation, 663 
painting, 663 
purpose of, 633 
riveting, 657 
stresses, 655 
thickness of plates, 657 
valves, 661 
wind-pressure, 655 
Stave-pipe, see Wooden pipe. 

Steam, as a disinfectant for wells and 
pipes, 134 

ooilers, efficiency of, 583 
engine, effect of condensers, 586 
effect of operating at part load, 588 
efficiency, 585 

expansive use of steam, 585 
steam-consumption, 587, 588 
expansive use of, 585 
Steel for pipes, 512 
stand-pipes, 656 
pipe, 511 

advantages, 511 
coating, 515 
corrosion, 516 
cost, 572 
details, 515 

distortion by back-filling, 500 
durability, 516 
expansion-joints, 556 
joints, 513, 515, 556 
laying, 555 

locking-bar joint, 515 
material for, 512 
riveting, 513 
stiffening of, 500 
stresses, 497 

temperature stresses, 500, 514 
thickness, 512 
Sterilization, 491 

Storage, impairment of water by, 169 
improvement of water by, 169 
of water, 311 

reservoirs, see Reservoirs, storage, 
tanks, see Tanks. 

Stored waters, 156 

diminution of dissolved oxygen in, 169 
Storms, great, 48 

Streams, flow of, see Flow of streams, 
gauging of, 248 

Street-sprinkling, water used for, 20 


Submerged pipes, 566 
Suction-pipes, 291, 612 
Sudbury aqueduct, coefficients for, 248 
Sulfate of alumina, action of, 408 
amount required, 409 
Sulfate of lime, solubility of, 481 
Sulfuric acid, use as disinfectant, 134 
Sunlight, effect of, on bacteria, 153 
Surface waters, 146 
appropriation of, 312 
as potable supplies, 146 
Surveys, sanitary, 137 
Synedra, 159, 160 
Syphon, inverted, 566 
ancient, 2 

Systems of supply, 201, 205 

separate for fire service, 205, 713 

Tanks, air-pressure, 677 
elevated, 665 

Ames, Iowa, 670, 671 
anchorage, 675 
details, 675 
dimensions, 665 
economy of, 665 
inlet-pipe, 675 
maintenance, 762 
masonry pedestal, 676 
Murphysboro, 673, 674 
stresses in, 666 
trestle tower, 669 
wooden, 676 
pressure, 677 
Tape-worms, 174 
Taste of water, 116 
Temperature of water, 116 
stresses, in pipes, 500, 514 
Temporary hardness, 143 
Thawing pipes, 721 
Thermophone, 117 
Tin-lined pipes, 529 
Tower, see Tanks, elevated. 
Transmission of energy, 590 
Trenching, 552, 713 
Tuberculation, 510 

effect on flow of water, 232 
Tunnels, as conduits, 546 
for collecting water, 305 
Turbidity, 115 

determination of, 115, 116 
Typhoid bacillus, in feces, 176 

methods of isolation, in water, 133 
relation of, to colon bacillus, 130, 174 
death-rates, decline in, coincident with 
improved water-supplies, 182, 185 
in cities on Great Lakes, 146 
Munich, 186 
river cities, 146 
Zurich, 185 

index of quality of water-supplies, 

fever, caused by polluted milk. 177 
caused by polluted wells, 181 
filters not complete protection, 429 




INDEX . 


745 


Typhoid fever, method of introduction, 
177 

mortality of, 178 
period of incubation, 177 
relation of sewers to, 177 
seasonal distribution, 186 
organism, difficulties in detecting, 132 
relation to colon organism, 130, 174 
vitality of, in ice, 160 
in water, 192 

outbreaks, Chicago, ’90-’g2, 181 
Havre, France, 164 
Lausen, Switzerland, 164 
Lowell-Lawrence, Mass.,'go-’gi, 180 
Mohawk-Hudson Valley, ’ 90-91, 179 
Plymouth, Pa., 183 
Stamford, Conn., 177 
Washington, D. C., 182 
Wittenberg, Germany, 164 

Units, chemical, 117 
hydraulic, 213 
Uroglena , 159 

Vacuum chambers, 612 
Valve-box, 559 
Valves, air, 560 

automatic, for pipe-lines, 562 
for stand-pipes, 662 
balanced, 452 
blow-off, 561 
filter-regulating, 451 
location of, 710 
loss of head in, 239 
maintenance, 722 
pump, 609, 
reservoir, 348, 379 
stop, 558 

Vapor tension, 214 
Venturi meter, 238 
Vitrified pipe, 527 
Volatile solids, 119 

Waste prevention, 722 
Waste-weirs, capacity, 352 
construction, 380 
examples, 381 
forms, 351, 380 
importance of, 326, 351 
Water, artesian, 16S 

consumption of, see Consumption of 
water. 

flow of, see Flow of water, 
flowing, 146 
impounded, 156 
measurement of, 237 
meteoric, 145 
pressure equivalents, 579 
spring, 164 
storage of, 311 
subterranean, 161 
surface, 146 
weight of, 213, 578 
well, 165 


Water analysis, interpretation of, 118 
value of different methods in, 112 
Water-borne diseases, 175 

relation to intestinal canal, 175 
Water-hammer, 242, 498 
Water-power, 582 

Water purification, see Purification of 
water. 

Water-ram, 242, 498 
Water-supplies, ancient, 1 
cost of, 729 

relation of, to disease, 173 
sources of, 36 
Water-table, defined, 84 
form of, 85 

Water-tower, masonry, 664, 676 ; see also 
Tanks. 

Water-vapor, pressure of, 214 
Water-weeds, effect of, on quality, 158 
Water-works, arrangement of, 199, 200 
classification, 199 
depreciation, 208, 210 
development in Europe, 9 
in U. S., 10 
Roman, 2, 7 

systems of operation, 201 
comparison of, 202 
double systems, 205, 713 
Water-works construction, cost compari¬ 
sons, 206 
economy of, 206 
estimates of cost, 211 
future provision, 210 
Water-works management, 727 
Waterphone, 724 
Waves, height of, 334 

pressure of, on dams, 369 
Weight of masonry, 361 
of water, 213 

Weirs, flow of water over, 218 
sharp-crested, 218 
submerged, 221 
various sections, 221 
Well, Joseph’s, I 
Well-points, 286 
strainers, 287 
Wells, ancient, I 

artesian, see Artesian wells, 
construction of, 280 
disinfection of, r34 
driven, see Wells, tubular, 
flow of water into, 267 
artesian, 273 
calculation of, 270, 276 
effect of fissures, 280 
size of well, 276 
formulas for, 268 
high-pressure, 277 
pipe-friction, 275 
forms of, 280 
horizontal, 307 
hydraulics of, 267 
large open, 282 
construction, 282 







INDEX. 


746 

Wells, large, cost of, 285 
examples, 284 
shoes for sinking, 283 
yield, 284 

large vs. small, 281 
location, 280 

of pumps in, 614 
near streams, 306 
pumps for, 614 
push, 307 
tubular, 285 
air-chambers, 292 
arrangement, 289 
Brooklyn, 295 
clogging of, 293 
connections, 291 
Cook, 287 
examples, 294 
operation, 289 
Plainfield, 294 
sand-box, 292 
sinking, 285 
size, 291 
spacing, 289 
strainers, 287 
suction mains, 291 
tests, 293 
well-points, 286 
yield, 290, 293 
yield of, 279 


Wells, yield of, decrease in, 279 
estimates of, 276 
Wire-rope transmission, 590 
Work and power equivalents, 579, 580 
Wood-stave pipe, friction in, 237 
Wooden pipe, 521 
advantages, 521 
bored pipe, 521 
construction, 555 
early use of, 10 
stave-pipe, 522 

bands for, 522, 523 
size, 523 
spacing, 524 
construction, 555 
coupling-shoes, 525 
cost, 572 
durability, 526 
leakage, 526 
specials, 525 
staves, 522 
Wyckoff pipe, 521 
Wooden tanks, 677 
maintenance, 719 
Worms, parasitic, 174 
Wrought-iron pipe, 511 
Wyckoff pipe, 521 

Zinc in water, 142, 529 
Zones of pressure, 709 




1 







-? 
































































